Nature Watch
December 27, 2007
By Susan Benson
Director of Education
Cable Natural History Museum
I saw the first white snowshoe hare of the season today. I was walking down near the Namekagon River when I noticed this white lump just inside the tree line along the road. There were still a few brown spots on the shoulder and back, but the hare had otherwise changed over to his beautiful, pure white winter coat that will eventually help it to disappear against the winter snow.
The change in fur color from brown to white in the fall and back again in the spring is just one difference between hares and rabbits, but it is the most easily observed. Because of this unique transition, the snowshoe hare is also known as the “varying hare.” Why do hares molt this way and rabbits do not? The answer is mostly related to climate.
The geographic ranges of hares and rabbits overlap here in Wisconsin, but hares are considered a northern species, while rabbits are a southern species. Farther north, the durations of summer and winter are more equal, so hares change colors to match their environment. The same is true of other far northern species, such as the weasels (which are also found in Wisconsin), ptarmigan, arctic fox, and collared lemmings. But the change in color has to also keep the hare warm, and white is typically known as a color that reflects sunlight. The answer to this riddle is that white in the natural world is not a color but is the absence of color, or pigment. The cells in white hairs are empty of pigment and are instead filled with air, which provides thermal insulation. The change from brown to white fur begins as the amount of daylight decreases. The ears and feet are the first to change, and the whole animal is white after about 10 weeks.
Snowshoe hares (waabooz in Ojibwemowin) are found in the northern half of Wisconsin where they prefer spruce and cedar swamps and other thickly-vegetated coniferous woodlands. Up to two litters of one to seven (usually two to four) hares are born each year between May and August. Hares primarily feed on grasses, tree buds, and other plant material, but they are also known to feed on the meat of dead animals, including other hares. They do not kill other animals, but they will scavenge carcasses whose insides have been exposed. Main predators of snowshoe hares in Wisconsin include weasels, gray and red foxes, coyotes, wolves, bobcats, and mink.
A popular topic of study for biologists has been the dramatic fluctuations of snowshoe hare populations. Hares are known to go from periods of great abundance (almost overabundance) to periods when there seem to be none left anywhere. The severity of the fluctuation varies geographically, and this is thought to be caused by the relative number of other species that occupy the same level as the hare in the food chain. In other words, if there are fewer links in the food chain (such as in far northern latitudes), and the hare is a main source of food for larger predators, than over-consumption by predators can cause the hare population to decline sharply, and the predator population will soon follow. On the other hand, if there are other animals (such as cottontail rabbits here in Wisconsin) for predators to feed on, then the hare population does not change so dramatically. It is estimated that as many as 85% of hares do not live for more than one year. The common life span for those that do survive is five years.
The change of seasons is upon us. The varying hare has shown that winter is indeed on the way, even if we do not see much snow yet. But the lack of snow makes it easier for us to see this fascinating animal if we look hard enough.
Nature Watch is brought to you by the Cable Natural History Museum. For 40 years, the Museum has served as a guide and mentor to generations of visitors and residents interested in learning to better appreciate and care for the extraordinary natural resources of the region. The Museum invites you to visit its facility in Cable at 43570 Kavanaugh Street or on the web at www.cablemuseum.org to learn more about exhibits and programs.
Thursday, December 27, 2007
Friday, December 21, 2007
This Food is for the Birds
Nature Watch
December 21, 2007
By Susan Benson
Director of Education
Cable Natural History Museum
I returned home late one evening last week and was walking up to the house when I heard it. Actually, I felt it more than I heard it. There was a deep resonant sound that beat in my chest. I stopped. It was about 25-degrees, and my breath formed small clouds as I stood in the driveway listening. Then, from out of the forest came a deep voice: Who’s awake? Me too. A quieter, single-note response followed from a second bird and then the silence returned. The male owl repeated his question and answer: Who’s awake? Me too, and the female bird responded again with a single note. After listening for a few minutes, I went into the house. It was clear that this conversation between a pair of Great Horned Owls would continue for a while.
There are eight species of owls that nest in Wisconsin, but only about half of them can be found in Bayfield County. The Great Horned Owl is perhaps the best known of these because it is found in every Wisconsin county, and because it is the most “owl-looking” owl. Even if people don’t know this common species by name, they likely think of it whenever someone says the word “owl.”
Great Horned Owls are large birds, nearly two-feet tall, with yellow eyes and feather tufts that stick up on each side of the head like ears. In our area, only the Barred Owl comes closest in height, standing 21-inches high. But Great Horned Owls can be distinguished from Barred Owls by their eyes. Barred Owls are one of only four species that have dark brown eyes rather than the piercing, bright yellow eyes found on the Great Horned and 14 other owl species in North America.
I heard the Great Horned Owls calling that evening because these dark nights and cold days of winter are the beginning of the mating season for them and most other owls. Adults are calling back and forth to each other, looking for mates and cementing relationships. They will soon be building nests and settling down to lay eggs and raise young. In Wisconsin, eggs are laid as early as February 6, and the first young are hatching a little over one month later.
Habitat for the Great Horned Owl varies from the deciduous woodlands between open grass- and croplands, to gaps within the heavily wooded northern forest. They feed on a wide variety of small birds, mammals, and snakes, but their favorite foods are mice and cottontail rabbits. Nests are typically made of large sticks, but the owls do not build a nest themselves. Instead, they will take one over that has been built by some other bird, usually Red-tailed Hawks, but sometimes ravens or the occasional squirrel. The Red-tailed Hawk nests are particularly favored because the hawks migrate and do not return before owl nesting begins. Great Horned Owls also nest in tree cavities and stumps, and even occasionally (but rarely) on the ground.
Great Horned Owls, like most of their other relatives, are most active at night. With a bit of searching, you might find one roosting high in a tree during the day, often sitting right next to the trunk. I once found one in Ashland’s Prentice Park, perched among the bare branches of an aspen tree. I could see its yellow eyes clearly burning right into me even from the great distance that separated us.
If you are fascinated by these birds like I am, you might want to join me on one of the “Owl Prowls” sponsored by the Cable Natural History Museum. One evening a month from June through October, I take people out into the woods to call for owls. Usually we only see Barred Owls, but we are sometimes lucky enough to find a Great Horned Owl or perhaps one of the more uncommon species such as the tiny Northern Saw-whet Owl. Incidentally, if you would like to hear an exchange between a male and female Great Horned Owl like the one I heard a few nights ago, you can find a recording from California on online at www.owling.com/Great_Horned.htm#recordings. Click on the recording labeled “Silverado Canyon, California, October 2000” on the far right. You can also hear the Great Horned Owl and the other species found in Wisconsin at the Museum’s Owl Booth, which is part of our “Birds in Focus” exhibit. Stop in and listen to “who’s awake?” and “who cooks for you all?”!
Nature Watch is brought to you by the Cable Natural History Museum. For 40 years, the Museum has served as a guide and mentor to generations of visitors and residents interested in learning to better appreciate and care for the extraordinary natural resources of the region. The Museum invites you to visit its facility in Cable at 43570 Kavanaugh Street or on the web at www.cablemuseum.org to learn more about exhibits and programs.
December 21, 2007
By Susan Benson
Director of Education
Cable Natural History Museum
I returned home late one evening last week and was walking up to the house when I heard it. Actually, I felt it more than I heard it. There was a deep resonant sound that beat in my chest. I stopped. It was about 25-degrees, and my breath formed small clouds as I stood in the driveway listening. Then, from out of the forest came a deep voice: Who’s awake? Me too. A quieter, single-note response followed from a second bird and then the silence returned. The male owl repeated his question and answer: Who’s awake? Me too, and the female bird responded again with a single note. After listening for a few minutes, I went into the house. It was clear that this conversation between a pair of Great Horned Owls would continue for a while.
There are eight species of owls that nest in Wisconsin, but only about half of them can be found in Bayfield County. The Great Horned Owl is perhaps the best known of these because it is found in every Wisconsin county, and because it is the most “owl-looking” owl. Even if people don’t know this common species by name, they likely think of it whenever someone says the word “owl.”
Great Horned Owls are large birds, nearly two-feet tall, with yellow eyes and feather tufts that stick up on each side of the head like ears. In our area, only the Barred Owl comes closest in height, standing 21-inches high. But Great Horned Owls can be distinguished from Barred Owls by their eyes. Barred Owls are one of only four species that have dark brown eyes rather than the piercing, bright yellow eyes found on the Great Horned and 14 other owl species in North America.
I heard the Great Horned Owls calling that evening because these dark nights and cold days of winter are the beginning of the mating season for them and most other owls. Adults are calling back and forth to each other, looking for mates and cementing relationships. They will soon be building nests and settling down to lay eggs and raise young. In Wisconsin, eggs are laid as early as February 6, and the first young are hatching a little over one month later.
Habitat for the Great Horned Owl varies from the deciduous woodlands between open grass- and croplands, to gaps within the heavily wooded northern forest. They feed on a wide variety of small birds, mammals, and snakes, but their favorite foods are mice and cottontail rabbits. Nests are typically made of large sticks, but the owls do not build a nest themselves. Instead, they will take one over that has been built by some other bird, usually Red-tailed Hawks, but sometimes ravens or the occasional squirrel. The Red-tailed Hawk nests are particularly favored because the hawks migrate and do not return before owl nesting begins. Great Horned Owls also nest in tree cavities and stumps, and even occasionally (but rarely) on the ground.
Great Horned Owls, like most of their other relatives, are most active at night. With a bit of searching, you might find one roosting high in a tree during the day, often sitting right next to the trunk. I once found one in Ashland’s Prentice Park, perched among the bare branches of an aspen tree. I could see its yellow eyes clearly burning right into me even from the great distance that separated us.
If you are fascinated by these birds like I am, you might want to join me on one of the “Owl Prowls” sponsored by the Cable Natural History Museum. One evening a month from June through October, I take people out into the woods to call for owls. Usually we only see Barred Owls, but we are sometimes lucky enough to find a Great Horned Owl or perhaps one of the more uncommon species such as the tiny Northern Saw-whet Owl. Incidentally, if you would like to hear an exchange between a male and female Great Horned Owl like the one I heard a few nights ago, you can find a recording from California on online at www.owling.com/Great_Horned.htm#recordings. Click on the recording labeled “Silverado Canyon, California, October 2000” on the far right. You can also hear the Great Horned Owl and the other species found in Wisconsin at the Museum’s Owl Booth, which is part of our “Birds in Focus” exhibit. Stop in and listen to “who’s awake?” and “who cooks for you all?”!
Nature Watch is brought to you by the Cable Natural History Museum. For 40 years, the Museum has served as a guide and mentor to generations of visitors and residents interested in learning to better appreciate and care for the extraordinary natural resources of the region. The Museum invites you to visit its facility in Cable at 43570 Kavanaugh Street or on the web at www.cablemuseum.org to learn more about exhibits and programs.
Friday, December 14, 2007
December Birds
Nature Watch
Decemeber 14, 2007
By Susan Benson
Director of Education
Cable Natural History Museum
You may have noticed that the cold weather tends to dampen our cars’ fuel efficiency, meaning we have to burn more gas in winter than in summer to travel the same distance.
The same holds true for birds that spend winter in the cold north. Birds, like cars, run high-powered engines at hot temperatures—somewhere between 102 and 112 degrees Fahrenheit for most birds. They need a lot of energy to keep those engines burning, and this at a time when food is least available! How do they survive?
Their first goal is energy conservation, and birds go about this in a number of ways.
Birds have multiple layers of feathers that help them withstand the cold and maintain body temperature. When birds fluff up their feathers in the winter weather, they effectively double their feather volume, and this thick plumage traps an insulating layer of warm air next to their bodies. It would be as if your clothes magically changed into a puffy quilt when it got cold.
Feathers, however, do not protect a bird’s bill, legs and feet. Birds’ beaks are made of a hard material similar to their toenails that is not very vulnerable to harm from the cold. Exposed legs and feet, though, can suffer cold damage. This is where a clever adaptation allows many birds to survive the winter months, even when their legs and feet are in the icy water.
Here’s how it works: the large blood vessel carrying warm blood from the bird’s body into its leg separates into many smaller vessels. The vein carrying cooled blood back from the foot into the leg also divides into many smaller veins, which run alongside and between the blood vessels.
The birds move the heat from the warmer blood vessels to the cooler blood in the veins before the blood reaches the bird’s body—a strategy called “counter current heat exchange.” Birds also can condense the amount of blood entering the legs and feet by reducing the size of the arteries. These adaptations can decrease heat loss in legs and feet by as much as 90 percent.
Another trick birds practice is standing on one leg and lifting the other up into their breast feathers to keep it warm. Often you’ll see ducks in winter weather perched on the ground; when they do this, they wrap up their legs and feet in protective, warm feathers.
Additionally, many bird species that winter in the north can lower their heart rate, respiration, and metabolic rates to conserve heat and energy. Chickadees, for instance, drop their body temperatures from 10 to 20 degrees on very cold nights. Other birds wintering south of here, like some doves, swallows, hummingbirds, titmice, swifts, and nightjars, also can enter this state of dormancy, or torpor, to survive an unusually cold winter night.
During the cold winter nights, birds like woodpeckers and other species curl up inside tree cavities for cover and heat. Other birds crowd together in whatever nooks or crannies they find. Some species of birds that inhabit open fields in the winter months will burrow into snow holes to escape the winds and chill.
Of course, even with all these strategies of energy conservation in play, birds need to eat in order to replenish their energy. Fuel efficiency can only take you as far as you have fuel.
Some birds change their menus in winter. A nuthatch, for example, usually eats insects in summer, but changes its main dinner menu to seeds and nuts in the winter.
In a harsh winter, where snow and ice covers sources of seeds and insect larvae are hard to get to, many bids do die of starvation. This, of course, is why winter bird feeders can be so important in our region. If you have a chance, stop by the Cable Natural History Museum and see our exhibit “Birds in Focus.” It features a display of bird feeders, advice on feeding tactics, and many other resources that can help you learn about safely feeding birds through the winter.
Nature Watch is brought to you by the Cable Natural History Museum. For 40 years, the Museum has served as a guide and mentor to generations of visitors and residents interested in learning to better appreciate and care for the extraordinary natural resources of the region. The Museum invites you to visit its facility in Cable at 43570 Kavanaugh Street or on the web at www.cablemuseum.org to learn more about exhibits and programs.
Decemeber 14, 2007
By Susan Benson
Director of Education
Cable Natural History Museum
You may have noticed that the cold weather tends to dampen our cars’ fuel efficiency, meaning we have to burn more gas in winter than in summer to travel the same distance.
The same holds true for birds that spend winter in the cold north. Birds, like cars, run high-powered engines at hot temperatures—somewhere between 102 and 112 degrees Fahrenheit for most birds. They need a lot of energy to keep those engines burning, and this at a time when food is least available! How do they survive?
Their first goal is energy conservation, and birds go about this in a number of ways.
Birds have multiple layers of feathers that help them withstand the cold and maintain body temperature. When birds fluff up their feathers in the winter weather, they effectively double their feather volume, and this thick plumage traps an insulating layer of warm air next to their bodies. It would be as if your clothes magically changed into a puffy quilt when it got cold.
Feathers, however, do not protect a bird’s bill, legs and feet. Birds’ beaks are made of a hard material similar to their toenails that is not very vulnerable to harm from the cold. Exposed legs and feet, though, can suffer cold damage. This is where a clever adaptation allows many birds to survive the winter months, even when their legs and feet are in the icy water.
Here’s how it works: the large blood vessel carrying warm blood from the bird’s body into its leg separates into many smaller vessels. The vein carrying cooled blood back from the foot into the leg also divides into many smaller veins, which run alongside and between the blood vessels.
The birds move the heat from the warmer blood vessels to the cooler blood in the veins before the blood reaches the bird’s body—a strategy called “counter current heat exchange.” Birds also can condense the amount of blood entering the legs and feet by reducing the size of the arteries. These adaptations can decrease heat loss in legs and feet by as much as 90 percent.
Another trick birds practice is standing on one leg and lifting the other up into their breast feathers to keep it warm. Often you’ll see ducks in winter weather perched on the ground; when they do this, they wrap up their legs and feet in protective, warm feathers.
Additionally, many bird species that winter in the north can lower their heart rate, respiration, and metabolic rates to conserve heat and energy. Chickadees, for instance, drop their body temperatures from 10 to 20 degrees on very cold nights. Other birds wintering south of here, like some doves, swallows, hummingbirds, titmice, swifts, and nightjars, also can enter this state of dormancy, or torpor, to survive an unusually cold winter night.
During the cold winter nights, birds like woodpeckers and other species curl up inside tree cavities for cover and heat. Other birds crowd together in whatever nooks or crannies they find. Some species of birds that inhabit open fields in the winter months will burrow into snow holes to escape the winds and chill.
Of course, even with all these strategies of energy conservation in play, birds need to eat in order to replenish their energy. Fuel efficiency can only take you as far as you have fuel.
Some birds change their menus in winter. A nuthatch, for example, usually eats insects in summer, but changes its main dinner menu to seeds and nuts in the winter.
In a harsh winter, where snow and ice covers sources of seeds and insect larvae are hard to get to, many bids do die of starvation. This, of course, is why winter bird feeders can be so important in our region. If you have a chance, stop by the Cable Natural History Museum and see our exhibit “Birds in Focus.” It features a display of bird feeders, advice on feeding tactics, and many other resources that can help you learn about safely feeding birds through the winter.
Nature Watch is brought to you by the Cable Natural History Museum. For 40 years, the Museum has served as a guide and mentor to generations of visitors and residents interested in learning to better appreciate and care for the extraordinary natural resources of the region. The Museum invites you to visit its facility in Cable at 43570 Kavanaugh Street or on the web at www.cablemuseum.org to learn more about exhibits and programs.
Friday, December 7, 2007
Horns & Antlers
Nature Watch
December 7, 2007
By Susan Benson
Director of Education
Cable Natural History Museum
The nine-day gun-deer season has passed, but hunting continues to dominate conversations around town. Going into supermarkets, hardware stores, or gas stations, you can’t help but hear the stories, and those stories often include talk about antlers and horns. These two terms are often used interchangeably, but they actually are different physical structures. Antlers and horns, like hooves and claws, are both modified parts of the epidermal (skin) layer of mammals, but that is where the physical similarities end.
Horns are grown by both males and females in the family Bovidae (cows, sheep, and goats). They are modified bone covered by a cone-like layer of keratin, or modified hair tissue – the same material that forms our own hair and fingernails. Horns grow above the skull but below the skin, entirely separate structures that do eventually fuse to the skull during development. Horns are not shed each year, but are retained and, for many animals, continue to grow throughout life. Also, horns form a single tine and do not branch out. There is one exception to this rule. The pronghorn antelope (which is in a family separate from the cows, sheep, and goats) has horns that are branched, and it is the only horned mammal that annually sheds the keratin sheath that covers the horns.
Antlers are modified bones that do not have the keratin covering. Male deer, elk, and moose, which comprise the family Cervidae, grow antlers. The one exception to this is the caribou; both males and females of this species grow antlers. They are attached to the skull by way of a short base known as a pedicel. Antlers, unlike horns, are grown and then shed each year as the pedicel loses calcium, weakening its connection with the antler. Growth and development of antlers are controlled by hormones and, in the northern hemisphere, the increasing duration of daylight. The timing of the “drop” in the winter coincides with declining testosterone levels and decreasing daylight.
Antlers also have a covering over them, but it is not a permanent cover like the keratin sheath that grows over horns. The velvet that temporarily covers antlers as they grow is soft hair and skin that contains blood vessels and nerves. Growth of the antler stops and the velvet dies when testosterone levels reach their peak each fall. The velvet is then shed, in large part by the animal rubbing its antlers on trees and woody shrubs. This rubbing also polishes the antlers, which become stained by the blood that once pulsed through the vessels in the velvet.
Both horns and antlers are used by males to establish dominance and thereby gain access to females during the breeding season. Among the horned animals, males and females can be distinguished from one another by differences in the size of the horns. Male horns tend to be thicker at the base, while those on the females tend to be straighter and thinner, which may allow them to be used as a stabbing weapon.
Of course, there is variation among the horned animals, too. The horn of a rhinoceros is not considered a “true horn” because it is composed of epidermal cells and fibers rather than a bony core surrounded by a keratin sheath. The rhinoceros horn also does not grow from the skull, but from the tip of the snout. Giraffes also have horns. Their horns are composed of bone, and they arise from the skull like other “true horns,” but they do so from the rear of the skull rather than the front. Both male and female giraffes have horns, but unlike other horned animals, newborn young have them as well.
So if you are hunting and lucky enough to get a buck this season, or if you happen to find a skull or antlers during a walk in the woods, take a look at these fascinating structures. Compare them with horns (we have a few in the museum you can come and see) and you may be able to see some of the differences between them.
Nature Watch is brought to you by the Cable Natural History Museum. For 40 years, the Museum has served as a guide and mentor to generations of visitors and residents interested in learning to better appreciate and care for the extraordinary natural resources of the region. The Museum invites you to visit its facility in Cable at 43570 Kavanaugh Street or on the web at www.cablemuseum.org to learn more about exhibits and programs.
December 7, 2007
By Susan Benson
Director of Education
Cable Natural History Museum
The nine-day gun-deer season has passed, but hunting continues to dominate conversations around town. Going into supermarkets, hardware stores, or gas stations, you can’t help but hear the stories, and those stories often include talk about antlers and horns. These two terms are often used interchangeably, but they actually are different physical structures. Antlers and horns, like hooves and claws, are both modified parts of the epidermal (skin) layer of mammals, but that is where the physical similarities end.
Horns are grown by both males and females in the family Bovidae (cows, sheep, and goats). They are modified bone covered by a cone-like layer of keratin, or modified hair tissue – the same material that forms our own hair and fingernails. Horns grow above the skull but below the skin, entirely separate structures that do eventually fuse to the skull during development. Horns are not shed each year, but are retained and, for many animals, continue to grow throughout life. Also, horns form a single tine and do not branch out. There is one exception to this rule. The pronghorn antelope (which is in a family separate from the cows, sheep, and goats) has horns that are branched, and it is the only horned mammal that annually sheds the keratin sheath that covers the horns.
Antlers are modified bones that do not have the keratin covering. Male deer, elk, and moose, which comprise the family Cervidae, grow antlers. The one exception to this is the caribou; both males and females of this species grow antlers. They are attached to the skull by way of a short base known as a pedicel. Antlers, unlike horns, are grown and then shed each year as the pedicel loses calcium, weakening its connection with the antler. Growth and development of antlers are controlled by hormones and, in the northern hemisphere, the increasing duration of daylight. The timing of the “drop” in the winter coincides with declining testosterone levels and decreasing daylight.
Antlers also have a covering over them, but it is not a permanent cover like the keratin sheath that grows over horns. The velvet that temporarily covers antlers as they grow is soft hair and skin that contains blood vessels and nerves. Growth of the antler stops and the velvet dies when testosterone levels reach their peak each fall. The velvet is then shed, in large part by the animal rubbing its antlers on trees and woody shrubs. This rubbing also polishes the antlers, which become stained by the blood that once pulsed through the vessels in the velvet.
Both horns and antlers are used by males to establish dominance and thereby gain access to females during the breeding season. Among the horned animals, males and females can be distinguished from one another by differences in the size of the horns. Male horns tend to be thicker at the base, while those on the females tend to be straighter and thinner, which may allow them to be used as a stabbing weapon.
Of course, there is variation among the horned animals, too. The horn of a rhinoceros is not considered a “true horn” because it is composed of epidermal cells and fibers rather than a bony core surrounded by a keratin sheath. The rhinoceros horn also does not grow from the skull, but from the tip of the snout. Giraffes also have horns. Their horns are composed of bone, and they arise from the skull like other “true horns,” but they do so from the rear of the skull rather than the front. Both male and female giraffes have horns, but unlike other horned animals, newborn young have them as well.
So if you are hunting and lucky enough to get a buck this season, or if you happen to find a skull or antlers during a walk in the woods, take a look at these fascinating structures. Compare them with horns (we have a few in the museum you can come and see) and you may be able to see some of the differences between them.
Nature Watch is brought to you by the Cable Natural History Museum. For 40 years, the Museum has served as a guide and mentor to generations of visitors and residents interested in learning to better appreciate and care for the extraordinary natural resources of the region. The Museum invites you to visit its facility in Cable at 43570 Kavanaugh Street or on the web at www.cablemuseum.org to learn more about exhibits and programs.
Friday, November 30, 2007
Winter Birding
Nature Watch
November 30, 2007
By Susan Benson
Director of Education
Cable Natural History Museum
Winter has arrived, at least in the form of sustained cold temperatures. Many of us who live in the north enjoy the fact that we get four seasons, so bundle up and get outside if you can! Freezing temperatures tend to slow things down, but by no means do they bring wildlife activity to a stop. In fact, if you’ve always wanted to try birding, winter is a great time to start because there are fewer species around and they tend to congregate around feeders.
If you’re near a lake or river, you might also see birds congregating on open, ice-free water. Before everything freezes up, you might chance to see a swan, for example. Who can forget the classic tale of the ugly duckling, where a homely little chick grows into a beautiful white swan? That “duckling” in the story was no duck, of course, but was really a Mute Swan chick passing through its natural brownish phase before turning white.
The Mute Swan, commonly found along the East Coast and in parts of the Midwest, is the bird typically featured in artwork and folklore as a symbol of grace and beauty. However, many people consider this nonnative bird undesirable in North America because it harasses native waterfowl and can uproot large quantities of aquatic vegetation.
Mute Swans were brought to the United States from Eurasia in the 1800s as ornamental additions to estates, parks and zoos. Over the years, many were released or escaped captivity and, by the 1970s, a resident population had established itself in Wisconsin and has been growing ever since.
By contrast, native Trumpeter Swans were almost wiped out during the nineteenth century when they were hunted for their meat and feathers. Swan skins were sold in the fur trade to Europe where they were used to make ladies’ powder puffs and feathers were used to adorn fashionable hats. By 1900, it was widely believed that the species had become extinct. Fortunately, a small nonmigratory population of Trumpeters survived in remote mountain valleys of Montana, Idaho, and Wyoming. In the 1930s, a national effort was organized to protect these birds and in the decades since to reestablish populations in other states.
In 1989, trumpeter swans were reintroduced to Wisconsin and placed on the state endangered species list. State natural resource agencies in Minnesota and Michigan had also initiated Trumpeter Swan recovery programs in the 1980s, and together, the three states are now establishing flocks that will help create a migratory and breeding population in the Midwest.
Both the Trumpeter and Mute Swans can be found in marshes, lakes and prairies, and both are about the same size, with a wingspan of up to eight feet and weight of up to 30 pounds.
How can you tell the difference? The Mute Swan is best identified by its orange bill and prominent black fleshy knob extending from the base of the bill to the forehead. Additionally, Mute Swans typically hold their necks in an S-curve with the bill pointed downward. Contrary to its name, this bird is not silent, but utters a variety of calls, including grunts and snorts. By contrast, the Trumpeter Swan has a broad, black bill and holds its neck erect and head upright. True to its name, the Trumpeter’s voice sounds like a horn.
Start a winter birding journal this year! Chickadees, juncos, and nuthatches should easily get you started. Build your birding skills and confidence, then try to identify and get familiar with 10 bird species this winter.
Nature Watch is brought to you by the Cable Natural History Museum. For 40 years, the Museum has served as a guide and mentor to generations of visitors and residents interested in learning to better appreciate and care for the extraordinary natural resources of the region. The Museum invites you to visit its facility in Cable at 43570 Kavanaugh Street or on the web at www.cablemuseum.org to learn more about exhibits and programs.
November 30, 2007
By Susan Benson
Director of Education
Cable Natural History Museum
Winter has arrived, at least in the form of sustained cold temperatures. Many of us who live in the north enjoy the fact that we get four seasons, so bundle up and get outside if you can! Freezing temperatures tend to slow things down, but by no means do they bring wildlife activity to a stop. In fact, if you’ve always wanted to try birding, winter is a great time to start because there are fewer species around and they tend to congregate around feeders.
If you’re near a lake or river, you might also see birds congregating on open, ice-free water. Before everything freezes up, you might chance to see a swan, for example. Who can forget the classic tale of the ugly duckling, where a homely little chick grows into a beautiful white swan? That “duckling” in the story was no duck, of course, but was really a Mute Swan chick passing through its natural brownish phase before turning white.
The Mute Swan, commonly found along the East Coast and in parts of the Midwest, is the bird typically featured in artwork and folklore as a symbol of grace and beauty. However, many people consider this nonnative bird undesirable in North America because it harasses native waterfowl and can uproot large quantities of aquatic vegetation.
Mute Swans were brought to the United States from Eurasia in the 1800s as ornamental additions to estates, parks and zoos. Over the years, many were released or escaped captivity and, by the 1970s, a resident population had established itself in Wisconsin and has been growing ever since.
By contrast, native Trumpeter Swans were almost wiped out during the nineteenth century when they were hunted for their meat and feathers. Swan skins were sold in the fur trade to Europe where they were used to make ladies’ powder puffs and feathers were used to adorn fashionable hats. By 1900, it was widely believed that the species had become extinct. Fortunately, a small nonmigratory population of Trumpeters survived in remote mountain valleys of Montana, Idaho, and Wyoming. In the 1930s, a national effort was organized to protect these birds and in the decades since to reestablish populations in other states.
In 1989, trumpeter swans were reintroduced to Wisconsin and placed on the state endangered species list. State natural resource agencies in Minnesota and Michigan had also initiated Trumpeter Swan recovery programs in the 1980s, and together, the three states are now establishing flocks that will help create a migratory and breeding population in the Midwest.
Both the Trumpeter and Mute Swans can be found in marshes, lakes and prairies, and both are about the same size, with a wingspan of up to eight feet and weight of up to 30 pounds.
How can you tell the difference? The Mute Swan is best identified by its orange bill and prominent black fleshy knob extending from the base of the bill to the forehead. Additionally, Mute Swans typically hold their necks in an S-curve with the bill pointed downward. Contrary to its name, this bird is not silent, but utters a variety of calls, including grunts and snorts. By contrast, the Trumpeter Swan has a broad, black bill and holds its neck erect and head upright. True to its name, the Trumpeter’s voice sounds like a horn.
Start a winter birding journal this year! Chickadees, juncos, and nuthatches should easily get you started. Build your birding skills and confidence, then try to identify and get familiar with 10 bird species this winter.
Nature Watch is brought to you by the Cable Natural History Museum. For 40 years, the Museum has served as a guide and mentor to generations of visitors and residents interested in learning to better appreciate and care for the extraordinary natural resources of the region. The Museum invites you to visit its facility in Cable at 43570 Kavanaugh Street or on the web at www.cablemuseum.org to learn more about exhibits and programs.
Friday, November 23, 2007
Snowshoe Hare
Nature Watch
November 23, 2007
By Susan Benson
Director of Education
Cable Natural History Museum
I saw the first white snowshoe hare of the season today. I was walking down near the Namekagon River when I noticed this white lump just inside the tree line along the road. There were still a few brown spots on the shoulder and back, but the hare had otherwise changed over to his beautiful, pure white winter coat that will eventually help it to disappear against the winter snow.
The change in fur color from brown to white in the fall and back again in the spring is just one difference between hares and rabbits, but it is the most easily observed. Because of this unique transition, the snowshoe hare is also known as the “varying hare.” Why do hares molt this way and rabbits do not? The answer is mostly related to climate.
The geographic ranges of hares and rabbits overlap here in Wisconsin, but hares are considered a northern species, while rabbits are a southern species. Farther north, the durations of summer and winter are more equal, so hares change colors to match their environment. The same is true of other far northern species, such as the weasels (which are also found in Wisconsin), ptarmigan, arctic fox, and collared lemmings. But the change in color has to also keep the hare warm, and white is typically known as a color that reflects sunlight. The answer to this riddle is that white in the natural world is not a color but is the absence of color, or pigment. The cells in white hairs are empty of pigment and are instead filled with air, which provides thermal insulation. The change from brown to white fur begins as the amount of daylight decreases. The ears and feet are the first to change, and the whole animal is white after about 10 weeks.
Snowshoe hares (waabooz in Ojibwemowin) are found in the northern half of Wisconsin where they prefer spruce and cedar swamps and other thickly-vegetated coniferous woodlands. Up to two litters of one to seven (usually two to four) hares are born each year between May and August. Hares primarily feed on grasses, tree buds, and other plant material, but they are also known to feed on the meat of dead animals, including other hares. They do not kill other animals, but they will scavenge carcasses whose insides have been exposed. Main predators of snowshoe hares in Wisconsin include weasels, gray and red foxes, coyotes, wolves, bobcats, and mink.
A popular topic of study for biologists has been the dramatic fluctuations of snowshoe hare populations. Hares are known to go from periods of great abundance (almost overabundance) to periods when there seem to be none left anywhere. The severity of the fluctuation varies geographically, and this is thought to be caused by the relative number of other species that occupy the same level as the hare in the food chain. In other words, if there are fewer links in the food chain (such as in far northern latitudes), and the hare is a main source of food for larger predators, than over-consumption by predators can cause the hare population to decline sharply, and the predator population will soon follow. On the other hand, if there are other animals (such as cottontail rabbits here in Wisconsin) for predators to feed on, then the hare population does not change so dramatically. It is estimated that as many as 85% of hares do not live for more than one year. The common life span for those that do survive is five years.
The change of seasons is upon us. The varying hare has shown that winter is indeed on the way, even if we do not see much snow yet. But the lack of snow makes it easier for us to see this fascinating animal if we look hard enough.
Nature Watch is brought to you by the Cable Natural History Museum. For 40 years, the Museum has served as a guide and mentor to generations of visitors and residents interested in learning to better appreciate and care for the extraordinary natural resources of the region. The Museum invites you to visit its facility in Cable at 43570 Kavanaugh Street or on the web at www.cablemuseum.org to learn more about exhibits and programs.
November 23, 2007
By Susan Benson
Director of Education
Cable Natural History Museum
I saw the first white snowshoe hare of the season today. I was walking down near the Namekagon River when I noticed this white lump just inside the tree line along the road. There were still a few brown spots on the shoulder and back, but the hare had otherwise changed over to his beautiful, pure white winter coat that will eventually help it to disappear against the winter snow.
The change in fur color from brown to white in the fall and back again in the spring is just one difference between hares and rabbits, but it is the most easily observed. Because of this unique transition, the snowshoe hare is also known as the “varying hare.” Why do hares molt this way and rabbits do not? The answer is mostly related to climate.
The geographic ranges of hares and rabbits overlap here in Wisconsin, but hares are considered a northern species, while rabbits are a southern species. Farther north, the durations of summer and winter are more equal, so hares change colors to match their environment. The same is true of other far northern species, such as the weasels (which are also found in Wisconsin), ptarmigan, arctic fox, and collared lemmings. But the change in color has to also keep the hare warm, and white is typically known as a color that reflects sunlight. The answer to this riddle is that white in the natural world is not a color but is the absence of color, or pigment. The cells in white hairs are empty of pigment and are instead filled with air, which provides thermal insulation. The change from brown to white fur begins as the amount of daylight decreases. The ears and feet are the first to change, and the whole animal is white after about 10 weeks.
Snowshoe hares (waabooz in Ojibwemowin) are found in the northern half of Wisconsin where they prefer spruce and cedar swamps and other thickly-vegetated coniferous woodlands. Up to two litters of one to seven (usually two to four) hares are born each year between May and August. Hares primarily feed on grasses, tree buds, and other plant material, but they are also known to feed on the meat of dead animals, including other hares. They do not kill other animals, but they will scavenge carcasses whose insides have been exposed. Main predators of snowshoe hares in Wisconsin include weasels, gray and red foxes, coyotes, wolves, bobcats, and mink.
A popular topic of study for biologists has been the dramatic fluctuations of snowshoe hare populations. Hares are known to go from periods of great abundance (almost overabundance) to periods when there seem to be none left anywhere. The severity of the fluctuation varies geographically, and this is thought to be caused by the relative number of other species that occupy the same level as the hare in the food chain. In other words, if there are fewer links in the food chain (such as in far northern latitudes), and the hare is a main source of food for larger predators, than over-consumption by predators can cause the hare population to decline sharply, and the predator population will soon follow. On the other hand, if there are other animals (such as cottontail rabbits here in Wisconsin) for predators to feed on, then the hare population does not change so dramatically. It is estimated that as many as 85% of hares do not live for more than one year. The common life span for those that do survive is five years.
The change of seasons is upon us. The varying hare has shown that winter is indeed on the way, even if we do not see much snow yet. But the lack of snow makes it easier for us to see this fascinating animal if we look hard enough.
Nature Watch is brought to you by the Cable Natural History Museum. For 40 years, the Museum has served as a guide and mentor to generations of visitors and residents interested in learning to better appreciate and care for the extraordinary natural resources of the region. The Museum invites you to visit its facility in Cable at 43570 Kavanaugh Street or on the web at www.cablemuseum.org to learn more about exhibits and programs.
Wednesday, November 14, 2007
Snow Buntings
Nature Watch
November 14, 2007
By Susan Benson
Director of Education
Cable Natural History Museum
The snow buntings have arrived. You may have noticed the flocks of “little brown birds” along road shoulders and in open fields that are more white than brown. They are hard to see when they are on the ground, but when the flock takes flight, it looks as if a tuft of snow has blown up in the wind.
Snow buntings (Plectrophenax nivalis) are common winter visitors to the northern United States and the higher elevations of northern Colorado and Utah. They come to us from above the Arctic Circle, where they are found in Alaska, across northern Canada, Greenland, Iceland, and very northern Eurasia. They nest on tundra, rocky coastlines, and in the crevices and cracks of rocky mountain slopes. When they are here, we find them feeding on the seeds of grasses and other plants along roads, in fields, and along lakeshores, places most like the open tundra they are accustomed to further north. They are usually seen in flocks, often mixed with other winter birds such as horned larks.
Snow buntings are well-named. The species name nivalis comes from the Latin word, nivis, meaning “snow.” Adults have pure white heads, breasts, and bellies. Over the rest of the body, white is broken up by black on the back, shoulders, wing tips, and tail during the breeding season. Some of this coloration is retained over the winter, but when we see them here, the black has given way to more white on the back and tail along with some light tan on the head and back. Still, the white coloration is very striking, making this little bird difficult to confuse with any of the other winter finches.
Snow buntings are also well-named because, in our region, they portend the arrival of snow. Usually, when the snow buntings arrive, we see snow mixed with the rain or blowing in the cold north wind within a week. This year, just three days passed between my first sighting of the buntings and the first falling of snow. This is in contrast to the Koyukon people of northwestern Alaska who regard snow buntings as a sign of spring, “the certain proof that winter is vanquished at last,” according to writer and anthropologist Richard Nelson. But even in that far land, snow buntings are only visitors that “twitter over the drifts in April and vanish to places farther north a few weeks after [they] appear.”
How do such small birds survive in a bitterly cold place like the Arctic tundra? In her book, For the Birds, Laura Erickson writes that snow buntings can easily survive temperatures of 40 degrees below zero. But during periods of severe cold, the snow bunting, like the ruffed grouse, will stay warm by diving into a snow bank and burrowing in. Also, the black feathers on its back help the bunting to retain heat from the sun. Think of when you wear a black shirt on a sunny day. The black color absorbs light and heat, keeping you warmer than if you were wearing a lighter-colored shirt. Throughout the winter, buntings will use their bills to preen their feathers and they will “snow-bathe” flapping and rubbing in the snow. This actually causes the white and tan colors on their feathers to wear off, exposing the black feathers beneath. By spring, when they head north, the snow bunting is once again brilliantly black and white.
Snow buntings are just one of the winter visitors to our region. Others include the horned lark, common redpoll, pine siskin, and bohemian waxwing (the larger cousin of our resident cedar waxwing). Other, larger birds such as owls attract more attention, but the smaller snow bunting is one of the first to arrive, a special category for a beautiful little bird.
Nature Watch is brought to you by the Cable Natural History Museum. For 40 years, the Museum has served as a guide and mentor to generations of visitors and residents interested in learning to better appreciate and care for the extraordinary natural resources of the region. The Museum invites you to visit its facility in Cable at 43570 Kavanaugh Street or on the web at www.cablemuseum.org to learn more about exhibits and programs.
November 14, 2007
By Susan Benson
Director of Education
Cable Natural History Museum
The snow buntings have arrived. You may have noticed the flocks of “little brown birds” along road shoulders and in open fields that are more white than brown. They are hard to see when they are on the ground, but when the flock takes flight, it looks as if a tuft of snow has blown up in the wind.
Snow buntings (Plectrophenax nivalis) are common winter visitors to the northern United States and the higher elevations of northern Colorado and Utah. They come to us from above the Arctic Circle, where they are found in Alaska, across northern Canada, Greenland, Iceland, and very northern Eurasia. They nest on tundra, rocky coastlines, and in the crevices and cracks of rocky mountain slopes. When they are here, we find them feeding on the seeds of grasses and other plants along roads, in fields, and along lakeshores, places most like the open tundra they are accustomed to further north. They are usually seen in flocks, often mixed with other winter birds such as horned larks.
Snow buntings are well-named. The species name nivalis comes from the Latin word, nivis, meaning “snow.” Adults have pure white heads, breasts, and bellies. Over the rest of the body, white is broken up by black on the back, shoulders, wing tips, and tail during the breeding season. Some of this coloration is retained over the winter, but when we see them here, the black has given way to more white on the back and tail along with some light tan on the head and back. Still, the white coloration is very striking, making this little bird difficult to confuse with any of the other winter finches.
Snow buntings are also well-named because, in our region, they portend the arrival of snow. Usually, when the snow buntings arrive, we see snow mixed with the rain or blowing in the cold north wind within a week. This year, just three days passed between my first sighting of the buntings and the first falling of snow. This is in contrast to the Koyukon people of northwestern Alaska who regard snow buntings as a sign of spring, “the certain proof that winter is vanquished at last,” according to writer and anthropologist Richard Nelson. But even in that far land, snow buntings are only visitors that “twitter over the drifts in April and vanish to places farther north a few weeks after [they] appear.”
How do such small birds survive in a bitterly cold place like the Arctic tundra? In her book, For the Birds, Laura Erickson writes that snow buntings can easily survive temperatures of 40 degrees below zero. But during periods of severe cold, the snow bunting, like the ruffed grouse, will stay warm by diving into a snow bank and burrowing in. Also, the black feathers on its back help the bunting to retain heat from the sun. Think of when you wear a black shirt on a sunny day. The black color absorbs light and heat, keeping you warmer than if you were wearing a lighter-colored shirt. Throughout the winter, buntings will use their bills to preen their feathers and they will “snow-bathe” flapping and rubbing in the snow. This actually causes the white and tan colors on their feathers to wear off, exposing the black feathers beneath. By spring, when they head north, the snow bunting is once again brilliantly black and white.
Snow buntings are just one of the winter visitors to our region. Others include the horned lark, common redpoll, pine siskin, and bohemian waxwing (the larger cousin of our resident cedar waxwing). Other, larger birds such as owls attract more attention, but the smaller snow bunting is one of the first to arrive, a special category for a beautiful little bird.
Nature Watch is brought to you by the Cable Natural History Museum. For 40 years, the Museum has served as a guide and mentor to generations of visitors and residents interested in learning to better appreciate and care for the extraordinary natural resources of the region. The Museum invites you to visit its facility in Cable at 43570 Kavanaugh Street or on the web at www.cablemuseum.org to learn more about exhibits and programs.
Friday, November 9, 2007
Winter Questions
Nature Watch
November 9, 2007
By Susan Benson
Director of Education
Cable Natural History Museum
Well, we’ve got our first taste of it and more is around the corner: snow. Love it or hate it, snow is part of our lives here in the north, so let’s take a moment to think about and appreciate some of its unique properties.
Why is snow white?
Most natural materials absorb some wavelengths of sunlight and reflect others, which in turn gives these materials their color. Snow reflects most of the sunlight—and visible sunlight is white. The complex structure of snow crystals results in countless tiny surfaces from which visible light is reflected.
How big can snowflakes get?
Snowflakes are aggregations of many snow crystals. Most snowflakes are less than one-half inch across. Under certain conditions—usually involving near-freezing temperatures, light winds, and unstable atmospheric conditions—much larger and irregular flakes close to two inches across can form. No routine measure of snowflake dimensions are taken, so the exact answer is not known.
Is it ever too cold to snow?
It can snow even at incredibly cold temperatures as long as there is some source of moisture and some way to lift or cool the air. It is true, however, that most heavy snowfalls occur with relatively warm air temperatures near the ground—typically 15°F or warmer. Warmer air can hold more water vapor, and that vapor is what makes snow.
When is it too warm to snow?
Snow forms when the atmospheric temperature is at or below freezing and there is little moisture in the air. If the ground temperature is at or below freezing, of course the snow will reach the ground. However, snow can still reach the ground when the ground temperature is above freezing if the conditions are just right. In this case, snowflakes will begin to melt as they reach this warmer temperature layer; the melting creates evaporative cooling which cools the air immediately around the snow flake. This cooling retards melting. As a general rule, though, snow will not form if the groud temperature is 41°F or warmer.
Is it true that there is one inch of water in every ten inches of snow that falls?
The water content of snow is quite variable. While many snows that fall at temperatures close to 32°F and snows accompanied by strong winds do contain approximately one inch of water per 10 inches of snowfall, that ratio is not always accurate. Ten inches of fresh snow can contain as little as one-tenth of an inch of water or as much as four inches of water, depending on the snow’s crystal structure, the wind speed, temperature, and other factors.
Why is snow a good insulator?
Fresh, undisturbed snow is composed of a high percentage of air trapped among the lattice structure of the accumulated snow crystals. Since the air can barely move, heat transfer is greatly reduced. Fresh, uncompacted snow typically is 90-95 percent trapped air.
Why do weather forecasters have so much trouble forecasting snow?
Snow forecasting remains one of the more difficult challenges for meteorologists. One reason is that for many of the more intense snows, the heaviest snow amounts fall in surprisingly narrow bands that are on a smaller scale than observing networks and forecast zones. Also, extremely small temperature differences that define the boundary line between rain and snow make huge differences in snow forecasts.
Why does snow crunch when you step on it?
A layer of snow is composed of ice grains with air in between the ice grains. Because the snow layer is mostly empty air space, when you step on a layer of snow you compress that layer—a little or a lot, depending on how old the snow is. As the snow compresses, the ice grains rub against each other. This creates friction or resistance; the colder the temperature, the greater the friction between the grains of ice. The sudden squashing of the snow at lower temperatures produces the familiar creaking or crunching sound. At warmer temperatures—closer to melting—this friction is reduced to the point where the sliding of the grains against each other produces little or no noise. It’s difficult to say at what temperature the snow starts to crunch, but the colder the snow, the louder the crunch.
Nature Watch is brought to you by the Cable Natural History Museum. For 40 years, the Museum has served as a guide and mentor to generations of visitors and residents interested in learning to better appreciate and care for the extraordinary natural resources of the region. The Museum invites you to visit its facility in Cable at 43570 Kavanaugh Street or on the web at www.cablemuseum.org to learn more about exhibits and programs.
November 9, 2007
By Susan Benson
Director of Education
Cable Natural History Museum
Well, we’ve got our first taste of it and more is around the corner: snow. Love it or hate it, snow is part of our lives here in the north, so let’s take a moment to think about and appreciate some of its unique properties.
Why is snow white?
Most natural materials absorb some wavelengths of sunlight and reflect others, which in turn gives these materials their color. Snow reflects most of the sunlight—and visible sunlight is white. The complex structure of snow crystals results in countless tiny surfaces from which visible light is reflected.
How big can snowflakes get?
Snowflakes are aggregations of many snow crystals. Most snowflakes are less than one-half inch across. Under certain conditions—usually involving near-freezing temperatures, light winds, and unstable atmospheric conditions—much larger and irregular flakes close to two inches across can form. No routine measure of snowflake dimensions are taken, so the exact answer is not known.
Is it ever too cold to snow?
It can snow even at incredibly cold temperatures as long as there is some source of moisture and some way to lift or cool the air. It is true, however, that most heavy snowfalls occur with relatively warm air temperatures near the ground—typically 15°F or warmer. Warmer air can hold more water vapor, and that vapor is what makes snow.
When is it too warm to snow?
Snow forms when the atmospheric temperature is at or below freezing and there is little moisture in the air. If the ground temperature is at or below freezing, of course the snow will reach the ground. However, snow can still reach the ground when the ground temperature is above freezing if the conditions are just right. In this case, snowflakes will begin to melt as they reach this warmer temperature layer; the melting creates evaporative cooling which cools the air immediately around the snow flake. This cooling retards melting. As a general rule, though, snow will not form if the groud temperature is 41°F or warmer.
Is it true that there is one inch of water in every ten inches of snow that falls?
The water content of snow is quite variable. While many snows that fall at temperatures close to 32°F and snows accompanied by strong winds do contain approximately one inch of water per 10 inches of snowfall, that ratio is not always accurate. Ten inches of fresh snow can contain as little as one-tenth of an inch of water or as much as four inches of water, depending on the snow’s crystal structure, the wind speed, temperature, and other factors.
Why is snow a good insulator?
Fresh, undisturbed snow is composed of a high percentage of air trapped among the lattice structure of the accumulated snow crystals. Since the air can barely move, heat transfer is greatly reduced. Fresh, uncompacted snow typically is 90-95 percent trapped air.
Why do weather forecasters have so much trouble forecasting snow?
Snow forecasting remains one of the more difficult challenges for meteorologists. One reason is that for many of the more intense snows, the heaviest snow amounts fall in surprisingly narrow bands that are on a smaller scale than observing networks and forecast zones. Also, extremely small temperature differences that define the boundary line between rain and snow make huge differences in snow forecasts.
Why does snow crunch when you step on it?
A layer of snow is composed of ice grains with air in between the ice grains. Because the snow layer is mostly empty air space, when you step on a layer of snow you compress that layer—a little or a lot, depending on how old the snow is. As the snow compresses, the ice grains rub against each other. This creates friction or resistance; the colder the temperature, the greater the friction between the grains of ice. The sudden squashing of the snow at lower temperatures produces the familiar creaking or crunching sound. At warmer temperatures—closer to melting—this friction is reduced to the point where the sliding of the grains against each other produces little or no noise. It’s difficult to say at what temperature the snow starts to crunch, but the colder the snow, the louder the crunch.
Nature Watch is brought to you by the Cable Natural History Museum. For 40 years, the Museum has served as a guide and mentor to generations of visitors and residents interested in learning to better appreciate and care for the extraordinary natural resources of the region. The Museum invites you to visit its facility in Cable at 43570 Kavanaugh Street or on the web at www.cablemuseum.org to learn more about exhibits and programs.
Friday, November 2, 2007
Winter Coming
Nature Watch
November 2, 2007
By Susan Benson
Director of Education
Cable Natural History Museum
Chilly fall days give us a warning that winter is coming, and in response plants and animals (including we humans) adjustment accordingly.
The changing of the season also affects the behavior of bodies of water. You may have heard people referring to lakes “turning” this time of year, and wondered what that means.
It’s a twice-yearly phenomenon related to water and air temperature—here’s how it works: In late summer, lake surface waters reach their annual maximum temperatures. Deeper waters are cooler—in many lakes, there is a definite stratification or layering of water temperatures that you would feel if you were swimming on the surface and then dove down deep. The warmest, least dense waters lie on top; water temperature decreases with depth, reaching its minimum temperature at the greatest lake depths.
In the summer, a deep lake will have three layers in the water column: the upper, warmest water (the epilimnion); a thin middle layer, where temperatures rapidly decrease (the thermocline or mesolimnion); and the deepest, coldest water (hypolimnion).
In autumn, cooler air temperatures and diminished hours of sunlight result in a loss of heat from the lake’s upper water layer. As these waters cool, they become more dense and when they reach about 50 degrees F, they sink into the middle layer below, erasing the temperature stratification that had developed during summer.
Eventually, all the lake water reaches a uniform temperature, and surface winds then mix all the water. When the winds are strong and fairly constant in direction for an extended time, they establish a water circulation pattern—as surface waters are blown downwind, waters from below must rise along the upwind shore to replace those waters pushed across the surface. To complete the circuit, the downwind shore surface waters, piled up by the wind, sink to replace the rising bottom waters.
In time, the resulting circulations will completely overturn and mix all the lake’s water—hence “fall turning.” The phenomenon can at times produce a rotten-egg odor, since the deep waters, which are low in oxygen and high in sulphur, rise to the surface and release sulphurous gases into the air. The turnover also mixes atmospheric oxygen into the lake water, replenishing the oxygen in deep waters and allowing fish to return to the depths where many will spend the winter.
Of course, after the fall turning cools the lakewater and as winter approaches, surface waters approach the freezing mark. Unlike most compounds, water reaches its maximum density as a liquid just before becoming a solid. Under normal conditions, freshwater is most dense at 39 degrees F, and ice, being less dense than liquid water, floats. So as lake waters cool, they sink when they reach 39 degrees. Colder water remains above, and is eventually covered with ice.
In the spring, the cycle happens again in reverse. Ice cover melts, and cold surface waters warm until they reach the temperatures of the bottom waters. Winds blowing over the lake again set up a full circulation system; as warming continues, the three water layers again become established, and a full turn of the cycle is complete.
Nature Watch is brought to you by the Cable Natural History Museum. For 40 years, the Museum has served as a guide and mentor to generations of visitors and residents interested in learning to better appreciate and care for the extraordinary natural resources of the region. The Museum invites you to visit its facility in Cable at 43570 Kavanaugh Street or on the web at www.cablemuseum.org to learn more about exhibits and programs.
November 2, 2007
By Susan Benson
Director of Education
Cable Natural History Museum
Chilly fall days give us a warning that winter is coming, and in response plants and animals (including we humans) adjustment accordingly.
The changing of the season also affects the behavior of bodies of water. You may have heard people referring to lakes “turning” this time of year, and wondered what that means.
It’s a twice-yearly phenomenon related to water and air temperature—here’s how it works: In late summer, lake surface waters reach their annual maximum temperatures. Deeper waters are cooler—in many lakes, there is a definite stratification or layering of water temperatures that you would feel if you were swimming on the surface and then dove down deep. The warmest, least dense waters lie on top; water temperature decreases with depth, reaching its minimum temperature at the greatest lake depths.
In the summer, a deep lake will have three layers in the water column: the upper, warmest water (the epilimnion); a thin middle layer, where temperatures rapidly decrease (the thermocline or mesolimnion); and the deepest, coldest water (hypolimnion).
In autumn, cooler air temperatures and diminished hours of sunlight result in a loss of heat from the lake’s upper water layer. As these waters cool, they become more dense and when they reach about 50 degrees F, they sink into the middle layer below, erasing the temperature stratification that had developed during summer.
Eventually, all the lake water reaches a uniform temperature, and surface winds then mix all the water. When the winds are strong and fairly constant in direction for an extended time, they establish a water circulation pattern—as surface waters are blown downwind, waters from below must rise along the upwind shore to replace those waters pushed across the surface. To complete the circuit, the downwind shore surface waters, piled up by the wind, sink to replace the rising bottom waters.
In time, the resulting circulations will completely overturn and mix all the lake’s water—hence “fall turning.” The phenomenon can at times produce a rotten-egg odor, since the deep waters, which are low in oxygen and high in sulphur, rise to the surface and release sulphurous gases into the air. The turnover also mixes atmospheric oxygen into the lake water, replenishing the oxygen in deep waters and allowing fish to return to the depths where many will spend the winter.
Of course, after the fall turning cools the lakewater and as winter approaches, surface waters approach the freezing mark. Unlike most compounds, water reaches its maximum density as a liquid just before becoming a solid. Under normal conditions, freshwater is most dense at 39 degrees F, and ice, being less dense than liquid water, floats. So as lake waters cool, they sink when they reach 39 degrees. Colder water remains above, and is eventually covered with ice.
In the spring, the cycle happens again in reverse. Ice cover melts, and cold surface waters warm until they reach the temperatures of the bottom waters. Winds blowing over the lake again set up a full circulation system; as warming continues, the three water layers again become established, and a full turn of the cycle is complete.
Nature Watch is brought to you by the Cable Natural History Museum. For 40 years, the Museum has served as a guide and mentor to generations of visitors and residents interested in learning to better appreciate and care for the extraordinary natural resources of the region. The Museum invites you to visit its facility in Cable at 43570 Kavanaugh Street or on the web at www.cablemuseum.org to learn more about exhibits and programs.
Friday, October 26, 2007
Indian Summer
Nature Watch
October 26, 2007
By Susan Benson
Director of Education
Cable Natural History Museum
Although we’re now into November, we may still enjoy an occasional warm, dry day in the coming weeks. Of these sorts of days, the early American writer John Bradbury wrote: “The air is perfectly quiescent and all is stillness, as if Nature, after her exertions during the Summer, were now at rest.”
Such a warm spell is often called “Indian Summer,” a term that dates back to the 18th century in the United States. In general, it is defined as any spell of warm, quiet, hazy weather that may occur in October or November. Some people feel that a true Indian Summer can not occur until there has been a hard frost.
Where does the term “Indian Summer” come from? The earliest written usage was a passage in a letter written in 1778 by Frenchman named St. John de Crevecoeur. He wrote:
“Sometimes the rain is followed by an interval of calm and warmth which is called the Indian Summer; its characteristics are a tranquil atmosphere and general smokiness. Up to this epoch the approaches of winter are doubtful; it arrives about the middle of November, although snows and brief freezes often occur long before that date.”
But what do Indians have to do with it? One theory holds that early native Indians chose that time of year as their hunting season. The mild and hazy weather encourages animals to come out, and the haziness of the air might better enable hunters to sneak up on prey.
Another thought is that Indians at that time were known to have set fires to prairie grass, underbrush and woods, which would have added to hazy, smoky conditions. Other possible explanations include: Indians made use of the dry, hazy weather to attack settlers before winter set in; this time was the season of the Indian harvest; or, that the predominant southwest winds that accompanied the Indian Summer period were regarded by the Indians as a favor or blessing.
Yet another hypothesis, but one having nothing to do with Native Americans, suggests that ships at that time crossing the Indian Ocean loaded up their cargo the most during the “Indian Summer,” or fair weather season. Several ships actually had an “I.S.” on their hull at the load level thought safe during the Indian Summer.
Whatever the explanation, these rare warm, still days are indeed a blessing from nature before the rigors of winter set in—so should we happen to have a stretch of Indian Summer, get out and enjoy it!
You might also mark your calendars to get up early and get outside November 17-18 for the peak of the Leonid Meteor Shower. Visible might be as many as 10 meteors per hour and viewing will be best in the pre-dawn hours. The meteors will seem to originate out of the constellation Leo.
It’s not hard to practice phenology; it’s simply the study of changes in plants and animals as they respond to weather, climate, and the seasons. If you’re a gardener, hunter, bird watcher, nature photographer, or a generally outdoorsy person, you can probably also add “phenologist” to your list of titles.
Nature Watch is brought to you by the Cable Natural History Museum. For 40 years, the Museum has served as a guide and mentor to generations of visitors and residents interested in learning to better appreciate and care for the extraordinary natural resources of the region. The Museum invites you to visit its facility in Cable at 43570 Kavanaugh Street or on the web at www.cablemuseum.org to learn more about exhibits and programs.
October 26, 2007
By Susan Benson
Director of Education
Cable Natural History Museum
Although we’re now into November, we may still enjoy an occasional warm, dry day in the coming weeks. Of these sorts of days, the early American writer John Bradbury wrote: “The air is perfectly quiescent and all is stillness, as if Nature, after her exertions during the Summer, were now at rest.”
Such a warm spell is often called “Indian Summer,” a term that dates back to the 18th century in the United States. In general, it is defined as any spell of warm, quiet, hazy weather that may occur in October or November. Some people feel that a true Indian Summer can not occur until there has been a hard frost.
Where does the term “Indian Summer” come from? The earliest written usage was a passage in a letter written in 1778 by Frenchman named St. John de Crevecoeur. He wrote:
“Sometimes the rain is followed by an interval of calm and warmth which is called the Indian Summer; its characteristics are a tranquil atmosphere and general smokiness. Up to this epoch the approaches of winter are doubtful; it arrives about the middle of November, although snows and brief freezes often occur long before that date.”
But what do Indians have to do with it? One theory holds that early native Indians chose that time of year as their hunting season. The mild and hazy weather encourages animals to come out, and the haziness of the air might better enable hunters to sneak up on prey.
Another thought is that Indians at that time were known to have set fires to prairie grass, underbrush and woods, which would have added to hazy, smoky conditions. Other possible explanations include: Indians made use of the dry, hazy weather to attack settlers before winter set in; this time was the season of the Indian harvest; or, that the predominant southwest winds that accompanied the Indian Summer period were regarded by the Indians as a favor or blessing.
Yet another hypothesis, but one having nothing to do with Native Americans, suggests that ships at that time crossing the Indian Ocean loaded up their cargo the most during the “Indian Summer,” or fair weather season. Several ships actually had an “I.S.” on their hull at the load level thought safe during the Indian Summer.
Whatever the explanation, these rare warm, still days are indeed a blessing from nature before the rigors of winter set in—so should we happen to have a stretch of Indian Summer, get out and enjoy it!
You might also mark your calendars to get up early and get outside November 17-18 for the peak of the Leonid Meteor Shower. Visible might be as many as 10 meteors per hour and viewing will be best in the pre-dawn hours. The meteors will seem to originate out of the constellation Leo.
It’s not hard to practice phenology; it’s simply the study of changes in plants and animals as they respond to weather, climate, and the seasons. If you’re a gardener, hunter, bird watcher, nature photographer, or a generally outdoorsy person, you can probably also add “phenologist” to your list of titles.
Nature Watch is brought to you by the Cable Natural History Museum. For 40 years, the Museum has served as a guide and mentor to generations of visitors and residents interested in learning to better appreciate and care for the extraordinary natural resources of the region. The Museum invites you to visit its facility in Cable at 43570 Kavanaugh Street or on the web at www.cablemuseum.org to learn more about exhibits and programs.
Friday, October 19, 2007
Fall is Here
Nature Watch
October 19, 2007
By Susan Benson
Director of Education
Cable Natural History Museum
We continue our march toward winter! One sure sign is that when we step outside mornings and evenings, we can see our warm, moist breath condense in the chilly, drier air.
The same thing happens as plants and the ground itself “exhales” at night. All air contains moisture, which is called water vapor. The moisture in the air close to the ground comes from the soil and the plants; when this air cools at night, the moisture condenses to form water droplets on the grass and plants—what we call dew. When the temperature falls below freezing point, the moisture in the air freezes into ice crystals and settles on grass and plants—this is frost. Unlike dew, frost damages plants because the water inside the cells of a plant freezes and breaks the cells’ walls, resulting in the death of the affected part of that plant.
This cool fall air is still full of birds; many songbirds have already left the region, but you can still see ducks, Canada geese, woodcock, and snipe on the move, migrating south. Start watching for winter visitors arriving from Canada, like the dark-eyed junco and white-throated sparrow.
Another unmistakeable bird you might chance to see this fall is a wild turkey. The largest game bird in North America, turkeys were historically abundant in central and southern Wisconsin, and provided an important food source for Native Americans and early settlers. Wild turkeys were nearly eradicated from the state, but a successful reintroduction program begun in 1976 has led to healthy populations found throughout the southern two-thirds of Wisconsin.
It was thought that turkeys would not be able to survive in the northern part of the state, because long periods of snow cover would keep them from finding food. However, during the winter of 2003-04, 164 turkeys were released onto six sites in Bayfield and Ashland Counties, and due to a combination of the hardiness of this species, plus our recent mild winters, the turkeys have thrived and expanded their population and range in our region.
Out on Lake Superior, anglers have been pulling on their insulated waders and heading out around the mouths of tributary streams and rivers, hoping to catch coho salmon. At this time of year, cohos migrate from the lake and upstream to spawn.
This popular sport fish, sometimes called a silver salmon or sea trout, is not native to the Great Lakes, but was intentionally brought here to help reduce the populations of alewives (also not native) in Great Lakes waters. By the late 1960s, coho were regularly raised in hatcheries and stocked into the Great Lakes, and now for better or worse have become part of the lakes’ ecosystem.
Become a phenologist! Jot down on a wall calendar each day you see or hear geese outside, then note the day they finally all depart. Keep track of the date of the first snowfall, or the first subzero night, then compare those notes from year to year to make your own record of winter’s arrival.
Nature Watch is brought to you by the Cable Natural History Museum. For 40 years, the Museum has served as a guide and mentor to generations of visitors and residents interested in learning to better appreciate and care for the extraordinary natural resources of the region. The Museum invites you to visit its facility in Cable at 43570 Kavanaugh Street or on the web at www.cablemuseum.org to learn more about exhibits and programs.
October 19, 2007
By Susan Benson
Director of Education
Cable Natural History Museum
We continue our march toward winter! One sure sign is that when we step outside mornings and evenings, we can see our warm, moist breath condense in the chilly, drier air.
The same thing happens as plants and the ground itself “exhales” at night. All air contains moisture, which is called water vapor. The moisture in the air close to the ground comes from the soil and the plants; when this air cools at night, the moisture condenses to form water droplets on the grass and plants—what we call dew. When the temperature falls below freezing point, the moisture in the air freezes into ice crystals and settles on grass and plants—this is frost. Unlike dew, frost damages plants because the water inside the cells of a plant freezes and breaks the cells’ walls, resulting in the death of the affected part of that plant.
This cool fall air is still full of birds; many songbirds have already left the region, but you can still see ducks, Canada geese, woodcock, and snipe on the move, migrating south. Start watching for winter visitors arriving from Canada, like the dark-eyed junco and white-throated sparrow.
Another unmistakeable bird you might chance to see this fall is a wild turkey. The largest game bird in North America, turkeys were historically abundant in central and southern Wisconsin, and provided an important food source for Native Americans and early settlers. Wild turkeys were nearly eradicated from the state, but a successful reintroduction program begun in 1976 has led to healthy populations found throughout the southern two-thirds of Wisconsin.
It was thought that turkeys would not be able to survive in the northern part of the state, because long periods of snow cover would keep them from finding food. However, during the winter of 2003-04, 164 turkeys were released onto six sites in Bayfield and Ashland Counties, and due to a combination of the hardiness of this species, plus our recent mild winters, the turkeys have thrived and expanded their population and range in our region.
Out on Lake Superior, anglers have been pulling on their insulated waders and heading out around the mouths of tributary streams and rivers, hoping to catch coho salmon. At this time of year, cohos migrate from the lake and upstream to spawn.
This popular sport fish, sometimes called a silver salmon or sea trout, is not native to the Great Lakes, but was intentionally brought here to help reduce the populations of alewives (also not native) in Great Lakes waters. By the late 1960s, coho were regularly raised in hatcheries and stocked into the Great Lakes, and now for better or worse have become part of the lakes’ ecosystem.
Become a phenologist! Jot down on a wall calendar each day you see or hear geese outside, then note the day they finally all depart. Keep track of the date of the first snowfall, or the first subzero night, then compare those notes from year to year to make your own record of winter’s arrival.
Nature Watch is brought to you by the Cable Natural History Museum. For 40 years, the Museum has served as a guide and mentor to generations of visitors and residents interested in learning to better appreciate and care for the extraordinary natural resources of the region. The Museum invites you to visit its facility in Cable at 43570 Kavanaugh Street or on the web at www.cablemuseum.org to learn more about exhibits and programs.
Friday, October 12, 2007
Fall Happenings
Nature Watch
October 12, 2007
By Susan Benson
Director of Education
Cable Natural History Museum
This is a great time for hiking! Most insects are gone, and most deciduous trees are now bare up here in the north woods, which means that if you’re walking through the woods, you get to see the countour of the landscape better than you would during the summer, when a full canopy of leaves hems in your field of vision.
It’s a great time for the young at heart to jump in leaf piles too. While you’re rolling around in the leaves, you might wonder what ultimately happens to fallen leaves. Unless they’re raked up and removed, leaves will break up and start decomposing into a layer on the forest floor that’s called humus.
Humus comes in two varieties, mor and mull. Mor humus is found in primarily coniferous forests whose floor is covered with a thick carpet of needles and leaves that decompose very slowly. Forces that decompose mor humus include fungi, springtails and mites; bacteria and earthworms are rare.
Mull humus is typical of deciduous forests—aspen, maple, birch, etc. Mull is either neutral or alkaline compared to the acidic mor humus, and the soil it creates tends to be rich and dark. In mull humus, bacteria are high in numbers, as are earthworms, slugs, millipedes, and lots of insect larvae.
On the edge of the forest, or in abandoned fields, you may notice milkweed plants, whose lavender summer flowers have now turned into large, slipper-shaped seed pods. The milkweed plants themselves grow from two to six feet high, and usually have a single, simple stem with opposing, oval-shaped leaves. The top surface of the leaves is smooth, but the bottom surface is hairy.
The plants’ large seed pods have a warty outer skin filled with downy fluff that will carry the seeds on the wind like a parachute. It’s said that this seed-fluff was used by Native Americans to insulate moccasins, and was also used as stuffing in military life jackets during World War II. The dried empty seed pods of the milkweed also were used as Christmas tree decorations by early pioneers.
Cattails are another plant that disperses its seeds in the fall via tiny parachutes on the wind. This wetland plant is very common to Wisconsin’s marshes, ponds, ditches, rivers and lakes. Cattails grow in dense groups, with up to ten-foot-tall sword-like leaves pointing up to the sky with a hearty stalk standing between them. Atop the stalk is the familiar long oval brown spike. Above the spike will appear a yellowish flower between May and July, but by September or October, after the flower has been pollinated, you’ll see the brown flower head pop open and get very fluffy. This means that the seeds are ripe and ready to float through the air in cottonball-like clumps, ready to start new plants.
You’re probably pulling out your cold-weather clothes and packing away the shorts and sandals for the season. Many animals do something similar, growing thicker coats of fur or adding insulation in the form of fat. The snowshoe hare has started to exchange its thin brown summer coat for thick, fluffy white fur that will provide camouflage as well as insulation for the snowy winter. The transformation starts with the ears and feet, and the full makeover takes about 10 weeks. Some people call this animal the “varying hare” because of this seasonal color change.
By the way, have you ever wondered if there is a difference between a rabbit and a hare? They are different: a snowshoe hare looks like a rabbit at first glance, but in general hares have longer ears, very large hind feet, and longer legs made for jumping. Hares are also born with their fur and their eyes open, unlike the rabbit. The snowshoe hare is slightly larger than the cottontail rabbit as well.
Nature Watch is brought to you by the Cable Natural History Museum. For 40 years, the Museum has served as a guide and mentor to generations of visitors and residents interested in learning to better appreciate and care for the extraordinary natural resources of the region. The Museum invites you to visit its facility in Cable at 43570 Kavanaugh Street or on the web at www.cablemuseum.org to learn more about exhibits and programs.
October 12, 2007
By Susan Benson
Director of Education
Cable Natural History Museum
This is a great time for hiking! Most insects are gone, and most deciduous trees are now bare up here in the north woods, which means that if you’re walking through the woods, you get to see the countour of the landscape better than you would during the summer, when a full canopy of leaves hems in your field of vision.
It’s a great time for the young at heart to jump in leaf piles too. While you’re rolling around in the leaves, you might wonder what ultimately happens to fallen leaves. Unless they’re raked up and removed, leaves will break up and start decomposing into a layer on the forest floor that’s called humus.
Humus comes in two varieties, mor and mull. Mor humus is found in primarily coniferous forests whose floor is covered with a thick carpet of needles and leaves that decompose very slowly. Forces that decompose mor humus include fungi, springtails and mites; bacteria and earthworms are rare.
Mull humus is typical of deciduous forests—aspen, maple, birch, etc. Mull is either neutral or alkaline compared to the acidic mor humus, and the soil it creates tends to be rich and dark. In mull humus, bacteria are high in numbers, as are earthworms, slugs, millipedes, and lots of insect larvae.
On the edge of the forest, or in abandoned fields, you may notice milkweed plants, whose lavender summer flowers have now turned into large, slipper-shaped seed pods. The milkweed plants themselves grow from two to six feet high, and usually have a single, simple stem with opposing, oval-shaped leaves. The top surface of the leaves is smooth, but the bottom surface is hairy.
The plants’ large seed pods have a warty outer skin filled with downy fluff that will carry the seeds on the wind like a parachute. It’s said that this seed-fluff was used by Native Americans to insulate moccasins, and was also used as stuffing in military life jackets during World War II. The dried empty seed pods of the milkweed also were used as Christmas tree decorations by early pioneers.
Cattails are another plant that disperses its seeds in the fall via tiny parachutes on the wind. This wetland plant is very common to Wisconsin’s marshes, ponds, ditches, rivers and lakes. Cattails grow in dense groups, with up to ten-foot-tall sword-like leaves pointing up to the sky with a hearty stalk standing between them. Atop the stalk is the familiar long oval brown spike. Above the spike will appear a yellowish flower between May and July, but by September or October, after the flower has been pollinated, you’ll see the brown flower head pop open and get very fluffy. This means that the seeds are ripe and ready to float through the air in cottonball-like clumps, ready to start new plants.
You’re probably pulling out your cold-weather clothes and packing away the shorts and sandals for the season. Many animals do something similar, growing thicker coats of fur or adding insulation in the form of fat. The snowshoe hare has started to exchange its thin brown summer coat for thick, fluffy white fur that will provide camouflage as well as insulation for the snowy winter. The transformation starts with the ears and feet, and the full makeover takes about 10 weeks. Some people call this animal the “varying hare” because of this seasonal color change.
By the way, have you ever wondered if there is a difference between a rabbit and a hare? They are different: a snowshoe hare looks like a rabbit at first glance, but in general hares have longer ears, very large hind feet, and longer legs made for jumping. Hares are also born with their fur and their eyes open, unlike the rabbit. The snowshoe hare is slightly larger than the cottontail rabbit as well.
Nature Watch is brought to you by the Cable Natural History Museum. For 40 years, the Museum has served as a guide and mentor to generations of visitors and residents interested in learning to better appreciate and care for the extraordinary natural resources of the region. The Museum invites you to visit its facility in Cable at 43570 Kavanaugh Street or on the web at www.cablemuseum.org to learn more about exhibits and programs.
Thursday, October 11, 2007
The Autumnal Equinox
Nature Watch
October 11, 2007
By Susan Benson
Director of Education
Cable Natural History Museum
The Autumnal Equinox occurred on September 22nd, officially marking, in astronomical terms, the beginning of autumn. Did you feel the difference? Probably not, but a huge change did occur.
The Autumnal Equinox marks the time when the sun moves south of the equator. We speak of this in terms of the sun, but the sun does not move; the change is actually brought about by the tilting of the earth. If you think of the earth as a person and North America as being on that person’s belly, the earth-person leans back during this time of year and points its belly into the darkness of space, away from the sun. The earth-person reclines further and further back throughout the winter, causing the sun’s daily peak height to be a little lower in the southern sky and the amount of daylight to progressively decrease. When the earth-person has tilted its belly as far as it can away from the sun, the sun is at its lowest point, or nadir. We mark this date with the Winter Solstice, which occurs around December 21st. This is the shortest day of the year and the first day of winter in the Northern Hemisphere.
The Winter Solstice also marks the point at which the earth-person begins tipping forward again. Eventually, the earth-person sits up straight, and its belt (the equator) is level with the sun. This happens around March 21st, the Vernal Equinox, or first day of spring (“vernal” means “spring”). Day and night are of equal length on this day. As the earth-person begins tipping forward and its belly comes closer to the sun, the sun moves north of the equator, the amount of daylight gradually increases, and the sun appears higher in the sky each day. It reaches its peak, or zenith, around June 21st, the Summer Solstice, which is the longest day of the year.
If that was a little tough to follow, maybe it will help to think of it this way. The word “equinox” means “equal night,” referring to the equal duration of light and darkness on the day of an equinox. More simply, equinox = equator. An equinox occurs when the sun crosses the equator, either headed south for the winter (the Autumnal Equinox) or north for the summer (the Vernal Equinox). On the other hand, “solstice” …… well, the word “solstice” does not lend itself to a clever memory trick; it just isn’t the equinox. It may help to know that the origin of the word “solstice” comes from the Latin for “sun stands still.” A solstice occurs when the sun reaches its highest or lowest point, its zenith or its nadir, and it marks the beginning of summer (at its zenith; the Summer Solstice) and the beginning of winter (at its nadir; the Winter Solstice).
Explanations for the cause and effects of the equinox and solstice are entirely scientific, but the occurrence of these changes holds great importance in many religious and cultural contexts. In general, the Autumnal Equinox marks the end of the harvest season and a time to reflect on the year as we light our home fires and approach the darkness of winter.
Nature Watch is brought to you by the Cable Natural History Museum. For 40 years, the Museum has served as a guide and mentor to generations of visitors and residents interested in learning to better appreciate and care for the extraordinary natural resources of the region. The Museum invites you to visit its facility in Cable at 43570 Kavanaugh Street or on the web at www.cablemuseum.org to learn more about exhibits and programs.
October 11, 2007
By Susan Benson
Director of Education
Cable Natural History Museum
The Autumnal Equinox occurred on September 22nd, officially marking, in astronomical terms, the beginning of autumn. Did you feel the difference? Probably not, but a huge change did occur.
The Autumnal Equinox marks the time when the sun moves south of the equator. We speak of this in terms of the sun, but the sun does not move; the change is actually brought about by the tilting of the earth. If you think of the earth as a person and North America as being on that person’s belly, the earth-person leans back during this time of year and points its belly into the darkness of space, away from the sun. The earth-person reclines further and further back throughout the winter, causing the sun’s daily peak height to be a little lower in the southern sky and the amount of daylight to progressively decrease. When the earth-person has tilted its belly as far as it can away from the sun, the sun is at its lowest point, or nadir. We mark this date with the Winter Solstice, which occurs around December 21st. This is the shortest day of the year and the first day of winter in the Northern Hemisphere.
The Winter Solstice also marks the point at which the earth-person begins tipping forward again. Eventually, the earth-person sits up straight, and its belt (the equator) is level with the sun. This happens around March 21st, the Vernal Equinox, or first day of spring (“vernal” means “spring”). Day and night are of equal length on this day. As the earth-person begins tipping forward and its belly comes closer to the sun, the sun moves north of the equator, the amount of daylight gradually increases, and the sun appears higher in the sky each day. It reaches its peak, or zenith, around June 21st, the Summer Solstice, which is the longest day of the year.
If that was a little tough to follow, maybe it will help to think of it this way. The word “equinox” means “equal night,” referring to the equal duration of light and darkness on the day of an equinox. More simply, equinox = equator. An equinox occurs when the sun crosses the equator, either headed south for the winter (the Autumnal Equinox) or north for the summer (the Vernal Equinox). On the other hand, “solstice” …… well, the word “solstice” does not lend itself to a clever memory trick; it just isn’t the equinox. It may help to know that the origin of the word “solstice” comes from the Latin for “sun stands still.” A solstice occurs when the sun reaches its highest or lowest point, its zenith or its nadir, and it marks the beginning of summer (at its zenith; the Summer Solstice) and the beginning of winter (at its nadir; the Winter Solstice).
Explanations for the cause and effects of the equinox and solstice are entirely scientific, but the occurrence of these changes holds great importance in many religious and cultural contexts. In general, the Autumnal Equinox marks the end of the harvest season and a time to reflect on the year as we light our home fires and approach the darkness of winter.
Nature Watch is brought to you by the Cable Natural History Museum. For 40 years, the Museum has served as a guide and mentor to generations of visitors and residents interested in learning to better appreciate and care for the extraordinary natural resources of the region. The Museum invites you to visit its facility in Cable at 43570 Kavanaugh Street or on the web at www.cablemuseum.org to learn more about exhibits and programs.
Friday, October 5, 2007
Autumnal Equinox
Nature Watch
October 5, 2007
By Susan Benson
Director of Education
Cable Natural History Museum
The Autumnal Equinox occurred on September 22, officially marking, in astronomical terms, the beginning of autumn. Did you feel the difference? Probably not, but a huge change did occur.
The Autumnal Equinox marks the time when the sun moves south of the equator. We speak of this in terms of the sun, but the sun does not move; the change is actually brought about by the tilting of the earth. If you think of the earth as a person and North America as being on that person’s belly, the earth-person leans back during this time of year and points its belly into the darkness of space, away from the sun. The earth-person reclines further and further back throughout the winter, causing the sun’s daily peak height to be a little lower in the southern sky and the amount of daylight to progressively decrease. When the earth-person has tilted its belly as far as it can away from the sun, the sun is at its lowest point, or nadir. We mark this date with the Winter Solstice, which occurs around December 21st. This is the shortest day of the year and the first day of winter in the Northern Hemisphere.
The Winter Solstice also marks the point at which the earth-person begins tipping forward again. Eventually, the earth-person sits up straight, and its belt (the equator) is level with the sun. This happens around March 21st, the Vernal Equinox, or first day of spring (“vernal” means “spring”). Day and night are of equal length on this day. As the earth-person begins tipping forward and its belly comes closer to the sun, the sun moves north of the equator, the amount of daylight gradually increases, and the sun appears higher in the sky each day. It reaches its peak, or zenith, around June 21st, the Summer Solstice, which is the longest day of the year.
If that was a little tough to follow, maybe it will help to think of it this way. The word “equinox” means “equal night,” referring to the equal duration of light and darkness on the day of an equinox. More simply, equinox = equator. An equinox occurs when the sun crosses the equator, either headed south for the winter (the Autumnal Equinox) or north for the summer (the Vernal Equinox). On the other hand, “solstice” …… well, the word “solstice” does not lend itself to a clever memory trick; it just isn’t the equinox. It may help to know that the origin of the word “solstice” comes from the Latin for “sun stands still.” A solstice occurs when the sun reaches its highest or lowest point, its zenith or its nadir, and it marks the beginning of summer (at its zenith; the Summer Solstice) and the beginning of winter (at its nadir; the Winter Solstice).
Explanations for the cause and effects of the equinox and solstice are entirely scientific, but the occurrence of these changes holds great importance in many religious and cultural contexts. In general, the Autumnal Equinox marks the end of the harvest season and a time to reflect on the year as we light our home fires and approach the darkness of winter.
Nature Watch is brought to you by the Cable Natural History Museum. For 40 years, the Museum has served as a guide and mentor to generations of visitors and residents interested in learning to better appreciate and care for the extraordinary natural resources of the region. The Museum invites you to visit its facility in Cable at 43570 Kavanaugh Street or on the web at www.cablemuseum.org to learn more about exhibits and programs.
October 5, 2007
By Susan Benson
Director of Education
Cable Natural History Museum
The Autumnal Equinox occurred on September 22, officially marking, in astronomical terms, the beginning of autumn. Did you feel the difference? Probably not, but a huge change did occur.
The Autumnal Equinox marks the time when the sun moves south of the equator. We speak of this in terms of the sun, but the sun does not move; the change is actually brought about by the tilting of the earth. If you think of the earth as a person and North America as being on that person’s belly, the earth-person leans back during this time of year and points its belly into the darkness of space, away from the sun. The earth-person reclines further and further back throughout the winter, causing the sun’s daily peak height to be a little lower in the southern sky and the amount of daylight to progressively decrease. When the earth-person has tilted its belly as far as it can away from the sun, the sun is at its lowest point, or nadir. We mark this date with the Winter Solstice, which occurs around December 21st. This is the shortest day of the year and the first day of winter in the Northern Hemisphere.
The Winter Solstice also marks the point at which the earth-person begins tipping forward again. Eventually, the earth-person sits up straight, and its belt (the equator) is level with the sun. This happens around March 21st, the Vernal Equinox, or first day of spring (“vernal” means “spring”). Day and night are of equal length on this day. As the earth-person begins tipping forward and its belly comes closer to the sun, the sun moves north of the equator, the amount of daylight gradually increases, and the sun appears higher in the sky each day. It reaches its peak, or zenith, around June 21st, the Summer Solstice, which is the longest day of the year.
If that was a little tough to follow, maybe it will help to think of it this way. The word “equinox” means “equal night,” referring to the equal duration of light and darkness on the day of an equinox. More simply, equinox = equator. An equinox occurs when the sun crosses the equator, either headed south for the winter (the Autumnal Equinox) or north for the summer (the Vernal Equinox). On the other hand, “solstice” …… well, the word “solstice” does not lend itself to a clever memory trick; it just isn’t the equinox. It may help to know that the origin of the word “solstice” comes from the Latin for “sun stands still.” A solstice occurs when the sun reaches its highest or lowest point, its zenith or its nadir, and it marks the beginning of summer (at its zenith; the Summer Solstice) and the beginning of winter (at its nadir; the Winter Solstice).
Explanations for the cause and effects of the equinox and solstice are entirely scientific, but the occurrence of these changes holds great importance in many religious and cultural contexts. In general, the Autumnal Equinox marks the end of the harvest season and a time to reflect on the year as we light our home fires and approach the darkness of winter.
Nature Watch is brought to you by the Cable Natural History Museum. For 40 years, the Museum has served as a guide and mentor to generations of visitors and residents interested in learning to better appreciate and care for the extraordinary natural resources of the region. The Museum invites you to visit its facility in Cable at 43570 Kavanaugh Street or on the web at www.cablemuseum.org to learn more about exhibits and programs.
Friday, September 28, 2007
Fall is here
Nature Watch
September 28, 2007
By Susan Benson
Director of Education
Cable Natural History Museum
After the glory of autumn color comes the inevitable bare-limbed look of our forests as leaves fall from hardwood trees. Ever wonder what triggers those leaves to fall?
It’s due to a chemical called auxin, a growth-regulating substance produced by plants. When leaves develop in the spring, each new leaf makes large amounts of auxin, which among other things, signals the leaf stem to grip its branch tightly. As the leaves age, they produce less auxin. As summer wears on, two thin layers of cells called the abscission layer grow across the base of the leaf stem where it is connected to the branch; this is likely initiated by the decreasing daily light period.
As the supply of auxin dwindles, the cells in the abscission layer separate from one another, and the leaf stem’s hold on the branch grows weaker. A hard rain or a gust of wind then blows the leaf free and it falls to the ground.
Even though we’ve had frost, there is still some harvest to be had among gardens and orchards. October is harvest time for animals as well as humans; many animals now are very active storing and hoarding food. From chickadees to voles to red squirrels to beaver, an animal’s success at finding and caching food will likely mean the difference between starvation and survival in the upcoming winter.
Storing up food is a full-time job. A pair of adult beavers typically stockpiles half a ton of tree branches to provide for their families through the winter. Red squirrels have been known to stash 15,000 cones along with hundreds of mushrooms in tree cavities and holes to tide them over.
Black bears also are quite active now, packing in the calories in preparation for upcoming hibernation. During the fall, bears are in a food frenzy—they eat constantly and may gain up to a third of their body weight in this season. In the fall, a hungry black bear might eat more than 20,000 calories per day. Compare that to the average human’s daily intake of 2,000-2,500 calories!
Throughout most of their range, black bears crawl into their winter dens between mid-October and mid-November. Individual bears choose denning times depending on food availability in the fall as well as their own physical condition. Female black bears, with or without cubs, tend to den up before males.
Become a phenologist! The cooler weather and occasional frost this time of year mean biting insects are not much of a bother—it’s an ideal time to hike or explore in the woods, and notice how plants and animals are preparing for the coming winter.
Nature Watch is brought to you by the Cable Natural History Museum. For 40 years, the Museum has served as a guide and mentor to generations of visitors and residents interested in learning to better appreciate and care for the extraordinary natural resources of the region. The Museum invites you to visit its facility in Cable at 43570 Kavanaugh Street or on the web at www.cablemuseum.org to learn more about exhibits and programs.
September 28, 2007
By Susan Benson
Director of Education
Cable Natural History Museum
After the glory of autumn color comes the inevitable bare-limbed look of our forests as leaves fall from hardwood trees. Ever wonder what triggers those leaves to fall?
It’s due to a chemical called auxin, a growth-regulating substance produced by plants. When leaves develop in the spring, each new leaf makes large amounts of auxin, which among other things, signals the leaf stem to grip its branch tightly. As the leaves age, they produce less auxin. As summer wears on, two thin layers of cells called the abscission layer grow across the base of the leaf stem where it is connected to the branch; this is likely initiated by the decreasing daily light period.
As the supply of auxin dwindles, the cells in the abscission layer separate from one another, and the leaf stem’s hold on the branch grows weaker. A hard rain or a gust of wind then blows the leaf free and it falls to the ground.
Even though we’ve had frost, there is still some harvest to be had among gardens and orchards. October is harvest time for animals as well as humans; many animals now are very active storing and hoarding food. From chickadees to voles to red squirrels to beaver, an animal’s success at finding and caching food will likely mean the difference between starvation and survival in the upcoming winter.
Storing up food is a full-time job. A pair of adult beavers typically stockpiles half a ton of tree branches to provide for their families through the winter. Red squirrels have been known to stash 15,000 cones along with hundreds of mushrooms in tree cavities and holes to tide them over.
Black bears also are quite active now, packing in the calories in preparation for upcoming hibernation. During the fall, bears are in a food frenzy—they eat constantly and may gain up to a third of their body weight in this season. In the fall, a hungry black bear might eat more than 20,000 calories per day. Compare that to the average human’s daily intake of 2,000-2,500 calories!
Throughout most of their range, black bears crawl into their winter dens between mid-October and mid-November. Individual bears choose denning times depending on food availability in the fall as well as their own physical condition. Female black bears, with or without cubs, tend to den up before males.
Become a phenologist! The cooler weather and occasional frost this time of year mean biting insects are not much of a bother—it’s an ideal time to hike or explore in the woods, and notice how plants and animals are preparing for the coming winter.
Nature Watch is brought to you by the Cable Natural History Museum. For 40 years, the Museum has served as a guide and mentor to generations of visitors and residents interested in learning to better appreciate and care for the extraordinary natural resources of the region. The Museum invites you to visit its facility in Cable at 43570 Kavanaugh Street or on the web at www.cablemuseum.org to learn more about exhibits and programs.
Friday, September 21, 2007
Fall Colors
Nature Watch
September 21, 2007
By Susan Benson
Director of Education
Cable Natural History Museum
What good is phenology? For some, it’s a year-round hobby that helps keep them in touch with the ebb and flow of the natural world. But the practice of noting and recording seasonal changes in nature does have what some would call more practical values.
For example, phenology is used to help with the prediction of insect emergence and strategies for insect control. Farmers, of course, are phenologists, and carefully correlate natural patterns and seasonal changes with crop planting and harvesting. Scientists who study global climate change trends pay close attention to the history of phenological data.
This time of year, the most obvious seasonal change is literally right in front of our eyes, as we are at the time of peak leaf color change among our deciduous trees.
The appearance of the beautiful yellows, reds, oranges we see is actually a result of the fading of the leafs’ green color, which is caused by cholorophyll. When chlorophyll fades, “beneath” it are other types of pigments that become revealed. These are the carotenoids, which produce yellow, orange, and brown colors; and the anthocyanins, which produce red, purple, and crimson colors.
The vibrancy of fall color is related to weather conditions that occur before and during the time when chlorophyll in the leaves is dwindling. A series of warm, sunny days and cool, crisp, but not freezing nights seems to bring about the most spectacular color displays.
Different tree species have characteristic color changes. Oak leaves usually turn red or brown. Aspens transform into golden yellow. Red maples turn brilliant scarlet and sugar maples change to an orange-red. Leaves of some species, such as the elm, just shrivel up and fall, while changing to a drab brown color.
The timing of the color change also varies by species. For example, oaks show their colors long after other species have already dropped their leaves. The differences in timing among species seems to be genetic, for a particular species at the same latitude will show the same coloration in high elevations at about the same time as it does in warmer lowlands.
Unique among the color-changing trees is the tamarack, also known as the eastern larch. In the spring and summer the tamarack has bright green flat, soft, and flexible needles. They are shaped uniquely on the branch in a whirled cluster somewhat like a flower’s petals. The trees are easy to identify by their narrow pyramid shape and their location—they’re most common in swampy areas.
This tree is both coniferous (produces cones) and deciduous (loses its leaves). Although the tamarack looks like an evergreen, it is not ever-green, because its needles change to a golden-yellow color in the fall and drop off.
On warm and sunny fall days, garter snakes can be found basking in the sun on rocks and fallen trees. Soon, they will find a rock pile or an abandoned ant hill where they’ll spend the winter in hibernation. This snake’s yellow stripes help camouflage it in the grasses of forests and open fields where it lives. The garter snake feeds on insects and small rodents like mice. It is not poisonous.
About this time, northern flying squirrels begin visiting oak trees to feed on acorns. As the acorns mature you might find partly chewed ones on the ground. The squirrels feed at night, so if you want to see them, look for the acorns then keep your eyes open for squirrels scrambling up the trees.
Become a phenologist! Take a fall hike and note all the different colors of the forest. Gather wild apples and make your own applesauce or cider. Soak up the fleeting warmth of sunny fall days as we turn our thoughts to colder weather.
Nature Watch is brought to you by the Cable Natural History Museum. For 40 years, the Museum has served as a guide and mentor to generations of visitors and residents interested in learning to better appreciate and care for the extraordinary natural resources of the region. The Museum invites you to visit its facility in Cable at 43570 Kavanaugh Street or on the web at www.cablemuseum.org to learn more about exhibits and programs.
September 21, 2007
By Susan Benson
Director of Education
Cable Natural History Museum
What good is phenology? For some, it’s a year-round hobby that helps keep them in touch with the ebb and flow of the natural world. But the practice of noting and recording seasonal changes in nature does have what some would call more practical values.
For example, phenology is used to help with the prediction of insect emergence and strategies for insect control. Farmers, of course, are phenologists, and carefully correlate natural patterns and seasonal changes with crop planting and harvesting. Scientists who study global climate change trends pay close attention to the history of phenological data.
This time of year, the most obvious seasonal change is literally right in front of our eyes, as we are at the time of peak leaf color change among our deciduous trees.
The appearance of the beautiful yellows, reds, oranges we see is actually a result of the fading of the leafs’ green color, which is caused by cholorophyll. When chlorophyll fades, “beneath” it are other types of pigments that become revealed. These are the carotenoids, which produce yellow, orange, and brown colors; and the anthocyanins, which produce red, purple, and crimson colors.
The vibrancy of fall color is related to weather conditions that occur before and during the time when chlorophyll in the leaves is dwindling. A series of warm, sunny days and cool, crisp, but not freezing nights seems to bring about the most spectacular color displays.
Different tree species have characteristic color changes. Oak leaves usually turn red or brown. Aspens transform into golden yellow. Red maples turn brilliant scarlet and sugar maples change to an orange-red. Leaves of some species, such as the elm, just shrivel up and fall, while changing to a drab brown color.
The timing of the color change also varies by species. For example, oaks show their colors long after other species have already dropped their leaves. The differences in timing among species seems to be genetic, for a particular species at the same latitude will show the same coloration in high elevations at about the same time as it does in warmer lowlands.
Unique among the color-changing trees is the tamarack, also known as the eastern larch. In the spring and summer the tamarack has bright green flat, soft, and flexible needles. They are shaped uniquely on the branch in a whirled cluster somewhat like a flower’s petals. The trees are easy to identify by their narrow pyramid shape and their location—they’re most common in swampy areas.
This tree is both coniferous (produces cones) and deciduous (loses its leaves). Although the tamarack looks like an evergreen, it is not ever-green, because its needles change to a golden-yellow color in the fall and drop off.
On warm and sunny fall days, garter snakes can be found basking in the sun on rocks and fallen trees. Soon, they will find a rock pile or an abandoned ant hill where they’ll spend the winter in hibernation. This snake’s yellow stripes help camouflage it in the grasses of forests and open fields where it lives. The garter snake feeds on insects and small rodents like mice. It is not poisonous.
About this time, northern flying squirrels begin visiting oak trees to feed on acorns. As the acorns mature you might find partly chewed ones on the ground. The squirrels feed at night, so if you want to see them, look for the acorns then keep your eyes open for squirrels scrambling up the trees.
Become a phenologist! Take a fall hike and note all the different colors of the forest. Gather wild apples and make your own applesauce or cider. Soak up the fleeting warmth of sunny fall days as we turn our thoughts to colder weather.
Nature Watch is brought to you by the Cable Natural History Museum. For 40 years, the Museum has served as a guide and mentor to generations of visitors and residents interested in learning to better appreciate and care for the extraordinary natural resources of the region. The Museum invites you to visit its facility in Cable at 43570 Kavanaugh Street or on the web at www.cablemuseum.org to learn more about exhibits and programs.
Friday, September 14, 2007
Migration
Nature Watch
September 14, 2007
By Susan Benson
Director of Education
Cable Natural History Museum
We’re still in the thick of the season for bird migration. Though you may see many species “flocking up” as their departure time grows near, when do they actually take off?
The vast majority of birds migrate at night, so we usually don’t notice when they leave. For nighttime travelers like warblers, tanagers, vireos, orioles, kinglets, thrushes, many sparrows, catbirds, shorebirds, owls, herons, egrets, and waterfowl, study after study shows that migration is initiated 30 minutes to an hour after sunset.
Peak migration is usually from about 10 p.m. to midnight; the number of birds diminishes greatly four to six hours after sunset. Often in the hours before dawn, there are few to no birds aloft.
So why migrate at night? One hypothesis has to do with food and energy, and suggests that birds need to feed during the day before undertaking long flights. That makes sense since foraging at night for insects, seeds and berries would certainly be more difficult. However, some birds do forage and migrate at night, so there are exceptions.
The other explanation also has to do with energy. Nighttime migrants engage in powered flight—that is, they flap their wings rather than soar and glide in order to propel themselves. The nighttime atmosphere is cooler and less turbulent than during the day, so it’s easier and more energy efficient for birds to fly at night.
Powered migrants also generate enormous amounts of heat during flight; cooler night weather reduces loss of water that is used for stabilizing their body temperature. During long non-stop flights, the loss of water may in fact be more limiting than the loss of fat.
All that said, however, there are birds that migrate during the day. Some songbird species are true daytime migrants, like red-winged blackbirds, brown-headed cowbirds, grackles, finches, crows, and blue jays. Most of these species migrate much shorter distances than nocturnal migrants, so they tend to venture south with a series of short flights.
Soaring birds like hawks, pelicans, cranes, and swallows almost always migrate during the day. They depend on thermal updrafts to give them lift, and these warm funnels of wind are most available during the day.
Down in the forests and fields, one of our common wild neighbors is going through a traditional fall transformation. During the summer while his antlers grow, the male white tail deer socializes as part of a bachelor group. But as days shorten, his testosterone levels increase, his antlers harden and the velvet supplying blood to his antlers dries to a ragged sheath that falls off. He rubs off the remains, and from that time on he is a loner, focused on the mating season and using his keen senses to detect danger, rivals and receptive does.
The buck advertises his presence by leaving physical scrapes and signs. He applies scents from various parts of his body to broadcast his presence to other deer. Saliva, urine, and secretions from pre-orbital glands in front of his eyes, forehead glands at the base of his antlers, and tarsal glands on the insides of his hind legs all send aromatic messages to other deer.
Become a phenologist! Celebrate the autumnal equinox this September 23—that day when hours of day and night are equal and we officially enter the fall season. (“Equinox” means “equal night.”) Stay up a little later and bid farewell to departing migrant birds.
Nature Watch is brought to you by the Cable Natural History Museum. For 40 years, the Museum has served as a guide and mentor to generations of visitors and residents interested in learning to better appreciate and care for the extraordinary natural resources of the region. The Museum invites you to visit its facility in Cable at 43570 Kavanaugh Street or on the web at www.cablemuseum.org to learn more about exhibits and programs.
September 14, 2007
By Susan Benson
Director of Education
Cable Natural History Museum
We’re still in the thick of the season for bird migration. Though you may see many species “flocking up” as their departure time grows near, when do they actually take off?
The vast majority of birds migrate at night, so we usually don’t notice when they leave. For nighttime travelers like warblers, tanagers, vireos, orioles, kinglets, thrushes, many sparrows, catbirds, shorebirds, owls, herons, egrets, and waterfowl, study after study shows that migration is initiated 30 minutes to an hour after sunset.
Peak migration is usually from about 10 p.m. to midnight; the number of birds diminishes greatly four to six hours after sunset. Often in the hours before dawn, there are few to no birds aloft.
So why migrate at night? One hypothesis has to do with food and energy, and suggests that birds need to feed during the day before undertaking long flights. That makes sense since foraging at night for insects, seeds and berries would certainly be more difficult. However, some birds do forage and migrate at night, so there are exceptions.
The other explanation also has to do with energy. Nighttime migrants engage in powered flight—that is, they flap their wings rather than soar and glide in order to propel themselves. The nighttime atmosphere is cooler and less turbulent than during the day, so it’s easier and more energy efficient for birds to fly at night.
Powered migrants also generate enormous amounts of heat during flight; cooler night weather reduces loss of water that is used for stabilizing their body temperature. During long non-stop flights, the loss of water may in fact be more limiting than the loss of fat.
All that said, however, there are birds that migrate during the day. Some songbird species are true daytime migrants, like red-winged blackbirds, brown-headed cowbirds, grackles, finches, crows, and blue jays. Most of these species migrate much shorter distances than nocturnal migrants, so they tend to venture south with a series of short flights.
Soaring birds like hawks, pelicans, cranes, and swallows almost always migrate during the day. They depend on thermal updrafts to give them lift, and these warm funnels of wind are most available during the day.
Down in the forests and fields, one of our common wild neighbors is going through a traditional fall transformation. During the summer while his antlers grow, the male white tail deer socializes as part of a bachelor group. But as days shorten, his testosterone levels increase, his antlers harden and the velvet supplying blood to his antlers dries to a ragged sheath that falls off. He rubs off the remains, and from that time on he is a loner, focused on the mating season and using his keen senses to detect danger, rivals and receptive does.
The buck advertises his presence by leaving physical scrapes and signs. He applies scents from various parts of his body to broadcast his presence to other deer. Saliva, urine, and secretions from pre-orbital glands in front of his eyes, forehead glands at the base of his antlers, and tarsal glands on the insides of his hind legs all send aromatic messages to other deer.
Become a phenologist! Celebrate the autumnal equinox this September 23—that day when hours of day and night are equal and we officially enter the fall season. (“Equinox” means “equal night.”) Stay up a little later and bid farewell to departing migrant birds.
Nature Watch is brought to you by the Cable Natural History Museum. For 40 years, the Museum has served as a guide and mentor to generations of visitors and residents interested in learning to better appreciate and care for the extraordinary natural resources of the region. The Museum invites you to visit its facility in Cable at 43570 Kavanaugh Street or on the web at www.cablemuseum.org to learn more about exhibits and programs.
Friday, September 7, 2007
Summer's End
Nature Watch
September 7, 2007
By Susan Benson
Director of Education
Cable Natural History Museum
It may still feel like summer, but the birds know better. Migration is peaking for many species, especially broad-wing hawks, and there’s no better place to witness this than up in Duluth at the Hawk Ridge Bird Observatory.
Broad-wings can be seen passing through, with the right winds, in enormous numbers. Like most raptors, they are reluctant to cross large bodies of water. When they migrate south and encounter Lake Superior, the birds naturally veer southwest along the lakeshore.
Broad-wings migrate at high altitudes and seldom stop to hunt during the days of their travels. Because of their dependence on cold-blooded terrestrial prey species, they migrate all the way to Central and even South America. In order to conserve energy on their long journey, they float upward on vertical air currents as high as they can go, and then shoot forward. These air currents, called thermals or updrafts, often are found above rock outcrops, buildings, or parking lots—surfaces that heat the air above them.
When one broad-wing discovers a thermal or updraft, others quickly join it, all swirling upward in a “kettle.” Their migration is one of the most exciting spectacles of the natural world. The Hawk Ridge Bird Observatory’s popular Hawk Weekend is scheduled for September 21-23 this year. In addition to broad-wing hawks, you may see various other raptors, the rarest of which include the peregrine falcon and gyrfalcon.
Use your sense of sound to pick up another sign of summer’s end. You’re probably familiar with that persistent hum in the trees on warm summer afternoons. That’s made by an insect called a cicada, using a pair of drumskin-like organs on the base of its abdomen. These vibrate at a high speed, making the buzzing noise, when the male cicada calls for a mate. However, that mating call drops off in mid-September, so the sound of fall—at least where the cicada is concerned—is actually the sound of silence.
The colorful Monarch butterflies we’ve seen all summer are beginning their migration south now. While most butterflies don’t stray too far from the area where they hatched, the Monarch is an exceptional exception. Every fall, in what is one of the greatest long-distance feats in the natural world, millions of Monarch butterflies embark on a trek that will take them hundreds, and in some cases, thousands of miles to wintering grounds in central Mexico.
North American monarchs are actually members of a group of tropical butterflies called Danaids. Like other tropical butterflies, Monarchs cannot withstand the freezing temperatures we get in this part of the world. But somehow, this creature has developed the capacity to avoid the cold winters by migrating south. Unlike many migrants, Monarchs make the trip without benefit of experience; they only live long enough to make the trip once.
A fall treat in the flower world is the New England aster, which you might find in roadside ditches or meadows, and is a glory to the eye in the fall landscape when most other flowers are gone. The New England aster comes in various shades of purple and can reach a height of four feet.
Become a phenologist! Mark your calendar each day you see a Monarch butterfly, then note the last entry this season. Seek out the last of the season’s wildflowers on your next walk or hike. Find a natural way to bid farewell to another fine summer.
Nature Watch is brought to you by the Cable Natural History Museum. For 40 years, the Museum has served as a guide and mentor to generations of visitors and residents interested in learning to better appreciate and care for the extraordinary natural resources of the region. The Museum invites you to visit its facility in Cable at 43570 Kavanaugh Street or on the web at www.cablemuseum.org
September 7, 2007
By Susan Benson
Director of Education
Cable Natural History Museum
It may still feel like summer, but the birds know better. Migration is peaking for many species, especially broad-wing hawks, and there’s no better place to witness this than up in Duluth at the Hawk Ridge Bird Observatory.
Broad-wings can be seen passing through, with the right winds, in enormous numbers. Like most raptors, they are reluctant to cross large bodies of water. When they migrate south and encounter Lake Superior, the birds naturally veer southwest along the lakeshore.
Broad-wings migrate at high altitudes and seldom stop to hunt during the days of their travels. Because of their dependence on cold-blooded terrestrial prey species, they migrate all the way to Central and even South America. In order to conserve energy on their long journey, they float upward on vertical air currents as high as they can go, and then shoot forward. These air currents, called thermals or updrafts, often are found above rock outcrops, buildings, or parking lots—surfaces that heat the air above them.
When one broad-wing discovers a thermal or updraft, others quickly join it, all swirling upward in a “kettle.” Their migration is one of the most exciting spectacles of the natural world. The Hawk Ridge Bird Observatory’s popular Hawk Weekend is scheduled for September 21-23 this year. In addition to broad-wing hawks, you may see various other raptors, the rarest of which include the peregrine falcon and gyrfalcon.
Use your sense of sound to pick up another sign of summer’s end. You’re probably familiar with that persistent hum in the trees on warm summer afternoons. That’s made by an insect called a cicada, using a pair of drumskin-like organs on the base of its abdomen. These vibrate at a high speed, making the buzzing noise, when the male cicada calls for a mate. However, that mating call drops off in mid-September, so the sound of fall—at least where the cicada is concerned—is actually the sound of silence.
The colorful Monarch butterflies we’ve seen all summer are beginning their migration south now. While most butterflies don’t stray too far from the area where they hatched, the Monarch is an exceptional exception. Every fall, in what is one of the greatest long-distance feats in the natural world, millions of Monarch butterflies embark on a trek that will take them hundreds, and in some cases, thousands of miles to wintering grounds in central Mexico.
North American monarchs are actually members of a group of tropical butterflies called Danaids. Like other tropical butterflies, Monarchs cannot withstand the freezing temperatures we get in this part of the world. But somehow, this creature has developed the capacity to avoid the cold winters by migrating south. Unlike many migrants, Monarchs make the trip without benefit of experience; they only live long enough to make the trip once.
A fall treat in the flower world is the New England aster, which you might find in roadside ditches or meadows, and is a glory to the eye in the fall landscape when most other flowers are gone. The New England aster comes in various shades of purple and can reach a height of four feet.
Become a phenologist! Mark your calendar each day you see a Monarch butterfly, then note the last entry this season. Seek out the last of the season’s wildflowers on your next walk or hike. Find a natural way to bid farewell to another fine summer.
Nature Watch is brought to you by the Cable Natural History Museum. For 40 years, the Museum has served as a guide and mentor to generations of visitors and residents interested in learning to better appreciate and care for the extraordinary natural resources of the region. The Museum invites you to visit its facility in Cable at 43570 Kavanaugh Street or on the web at www.cablemuseum.org
Friday, August 31, 2007
Wild Rice
Nature Watch
August 31, 2007
By Susan Benson
Director of Education
Cable Natural History Museum
As summer winds to a close, hunters may be thinking of upcoming game seasons, but gatherers are equally anxious. Of special significance this time of year is the wild rice harvest.
Wild rice is an annual aquatic grass whose nutritious seeds serve as valuable food for waterfowl. The plants themselves provide roosting and resting areas to adult waterfowl and protective cover for young birds. Wild rice also provides habitat for snails, insects, and mammals, adding to the biological diversity of the wetlands where it is found. In addition, wild rice helps maintain water quality by binding loose soils, tying up nutrients and slowing winds across shallow wetlands. These factors can increase water clarity and reduce algae blooms.
But wildlife and water quality are not the only beneficiaries of wild rice—this plant has long been a staple food for Native Americans and early European explorers of the region. To the Ojibwa, the plant is called manoomin, a term derived from “Manitou,” meaning Great Spirit and “meenum,” meaning delicacy.
Today’s wild rice harvest methods remain similar to those used for centuries. The ripe grain is harvested from canoes or small boats with the use of smooth, wooden sticks. Generally, two people gather rice as a team; one moves the canoe through the rice bed using a long push-pole while the other uses the sticks to “knock” the grain from the plant seed heads into the boat.
If you’ve never tried ricing before, be sure to check with the DNR to see when the season is open, and to check if you need a license for the area in which you wish to rice. Wild rice flourishes best in shallow, flowing water such as rivers and flowages, and in the lakes that have an inlet and outlet. Even if you have no interest in ricing, rice beds are worth watching for the number of animals they attract.
Another botanical sign of late summer is, for some people, the onset of hayfever or the “summer cold.” It’s not really a cold, but rather a reaction to the pollen of ragweeds, whose small green flowers unleash huge amounts of pollen from late summer to early fall. Goldenrod is often blamed for the hayfever, but it is innocent of the charge. Because it is tall with large clusters of bright yellow flowers, and flourishes at the peak of the hayfever season, goldenrod often takes the undeserved blame for our sneezing and runny noses.
Through early fall, listen for the chirping calls of crickets and cicadas. Crickets make their songs by rubbing a sharp ridge on one wing against a rough spot on the other. As the cricket rubs, its wings start to vibrate, creating the sound. Cold-blooded field crickets need heat to warm up their instrumental wings. That’s why we hear their singing in late afternoons or early evenings in summer and early fall.
Male cicadas make their pulsating, high-pitched buzz to attract mates from high in the hardwood trees. But by the end of September, after they’ve mated and laid their eggs, the adult cicadas die.
Cicadas spend most of their life underground. Born in trees, young cicadas drop to the earth after they hatch and tunnel into the soil. They feed on root sap for 13 to17 years until they emerge from their dark burrows. In adult form, these insects can’t eat—they don’t even have mouths! Adult cicadas live only as long as it takes to mate and lay eggs.
Now, a warning: boxelder bugs may have a huge population explosion this fall. These insects flourish on 10-year cycles, and we’re now in the most active part of their reproductive cycle. Boxelder bugs are mostly black with red lines decorating their backs. Though they are not harmful, they can be a nuisance as they seek shelter in protected places, such as cracks or crevices in walls, doors, under windows and around foundations.
Become a phenologist! Next to spring, late summer through early fall is the most active times of year in terms of natural changes due to weather and season. As you think ahead and prepare for the coming fall, take note of how plants and animals around you do the same.
Nature Watch is brought to you by the Cable Natural History Museum. For 40 years, the Museum has served as a guide and mentor to generations of visitors and residents interested in learning to better appreciate and care for the extraordinary natural resources of the region. The Museum invites you to visit its facility in Cable at 43570 Kavanaugh Street or on the web at www.cablemuseum.org to learn more about exhibits and programs.
August 31, 2007
By Susan Benson
Director of Education
Cable Natural History Museum
As summer winds to a close, hunters may be thinking of upcoming game seasons, but gatherers are equally anxious. Of special significance this time of year is the wild rice harvest.
Wild rice is an annual aquatic grass whose nutritious seeds serve as valuable food for waterfowl. The plants themselves provide roosting and resting areas to adult waterfowl and protective cover for young birds. Wild rice also provides habitat for snails, insects, and mammals, adding to the biological diversity of the wetlands where it is found. In addition, wild rice helps maintain water quality by binding loose soils, tying up nutrients and slowing winds across shallow wetlands. These factors can increase water clarity and reduce algae blooms.
But wildlife and water quality are not the only beneficiaries of wild rice—this plant has long been a staple food for Native Americans and early European explorers of the region. To the Ojibwa, the plant is called manoomin, a term derived from “Manitou,” meaning Great Spirit and “meenum,” meaning delicacy.
Today’s wild rice harvest methods remain similar to those used for centuries. The ripe grain is harvested from canoes or small boats with the use of smooth, wooden sticks. Generally, two people gather rice as a team; one moves the canoe through the rice bed using a long push-pole while the other uses the sticks to “knock” the grain from the plant seed heads into the boat.
If you’ve never tried ricing before, be sure to check with the DNR to see when the season is open, and to check if you need a license for the area in which you wish to rice. Wild rice flourishes best in shallow, flowing water such as rivers and flowages, and in the lakes that have an inlet and outlet. Even if you have no interest in ricing, rice beds are worth watching for the number of animals they attract.
Another botanical sign of late summer is, for some people, the onset of hayfever or the “summer cold.” It’s not really a cold, but rather a reaction to the pollen of ragweeds, whose small green flowers unleash huge amounts of pollen from late summer to early fall. Goldenrod is often blamed for the hayfever, but it is innocent of the charge. Because it is tall with large clusters of bright yellow flowers, and flourishes at the peak of the hayfever season, goldenrod often takes the undeserved blame for our sneezing and runny noses.
Through early fall, listen for the chirping calls of crickets and cicadas. Crickets make their songs by rubbing a sharp ridge on one wing against a rough spot on the other. As the cricket rubs, its wings start to vibrate, creating the sound. Cold-blooded field crickets need heat to warm up their instrumental wings. That’s why we hear their singing in late afternoons or early evenings in summer and early fall.
Male cicadas make their pulsating, high-pitched buzz to attract mates from high in the hardwood trees. But by the end of September, after they’ve mated and laid their eggs, the adult cicadas die.
Cicadas spend most of their life underground. Born in trees, young cicadas drop to the earth after they hatch and tunnel into the soil. They feed on root sap for 13 to17 years until they emerge from their dark burrows. In adult form, these insects can’t eat—they don’t even have mouths! Adult cicadas live only as long as it takes to mate and lay eggs.
Now, a warning: boxelder bugs may have a huge population explosion this fall. These insects flourish on 10-year cycles, and we’re now in the most active part of their reproductive cycle. Boxelder bugs are mostly black with red lines decorating their backs. Though they are not harmful, they can be a nuisance as they seek shelter in protected places, such as cracks or crevices in walls, doors, under windows and around foundations.
Become a phenologist! Next to spring, late summer through early fall is the most active times of year in terms of natural changes due to weather and season. As you think ahead and prepare for the coming fall, take note of how plants and animals around you do the same.
Nature Watch is brought to you by the Cable Natural History Museum. For 40 years, the Museum has served as a guide and mentor to generations of visitors and residents interested in learning to better appreciate and care for the extraordinary natural resources of the region. The Museum invites you to visit its facility in Cable at 43570 Kavanaugh Street or on the web at www.cablemuseum.org to learn more about exhibits and programs.
Thursday, August 23, 2007
Late Summer
Nature Watch
August 23, 2007
By Susan Benson,
CNHM Director of Education
While gardeners are busy harvesting green beans, sweet corn, zucchini, eggplants, tomatoes, and peppers, seasonal changes in nature are occurring all around. A bumper crop of acorns is falling right now, and squirrels can be seen in a frantic scurry to collect them. We can also find small piles of broken and chewed pine cone bracts as squirrels have eaten the pine seeds and left the remains behind.
Even more fascinating is what occurs in the bird world this time of year. During these late summer days, migratory birds have been feeding heavily, increasing their body weight sometimes by as much as 100 percent as they store fat and protein. They are able to eat more food because their digestive organs actually increase in size (those that do not feed during migration actually shrink.) The birds’ reproductive organs actually atrophy and shrink as hormone levels fall with decreasing daylight. Flight muscles, heart, and lungs also increase in size.
Flocks of birds, especially red-winged blackbirds, are flying about in extremely large groups. The first nighthawks have been spotted flying through the evening sky. Crows and blue jays can be seen migrating in flocks of up to 200 birds. Grackles and robins are moving through, flying fast and straight through the sky. Migrating birds of prey can be seen circling on thermals, large bubbles of warm air rising in the sky. Migrating flickers fly through in swooping flight and sun themselves on roadsides.
Adult loons begin flying south in late August and early September. Chicks stay on the nesting lakes, feeding and taking their first test flights, until nearly ice-over. One day, they start running across the water, take flight, and head south, where they will stay for the next three years. Most loon chicks will eventually return to their original nesting lake or find one nearby. Some loons do not establish their nesting territory until they are five years old.
We are beginning to see geese and some ducks flying in a regular V-shaped formation. One theory as to why they fly in this v-shape is that all birds except the one in the lead can gain lift from the wing-tip angles produced by the bird in front of them. According to scientists, the most efficient flight would include a one-fourth wingspan distance from the bird in front of it. However, motion pictures of flocks in flight show that Canada geese do not travel in these types of formations. Some scientists believe that the formations geese do use enable the birds to maintain visual contact and avoid possible mid-air collisions.
Become a phenologist! Keep your eyes open for migrating birds. Try counting them as they move through and track the date and numbers you observe. To get a good count, try counting as many as you can in a short time (before they are out of sight), and then estimate what fraction of the flock you have counted and multiply.
Nature Watch is brought to you by the Cable Natural History Museum. For 40 years, the Museum has served as a guide and mentor to generations of visitors and residents interested in learning to better appreciate and care for the extraordinary natural resources of the region. The Museum invites you to visit its facility in Cable at 43570 Kavanaugh Street or on the web at www.cablemuseum.org to learn more about exhibits and programs.
August 23, 2007
By Susan Benson,
CNHM Director of Education
While gardeners are busy harvesting green beans, sweet corn, zucchini, eggplants, tomatoes, and peppers, seasonal changes in nature are occurring all around. A bumper crop of acorns is falling right now, and squirrels can be seen in a frantic scurry to collect them. We can also find small piles of broken and chewed pine cone bracts as squirrels have eaten the pine seeds and left the remains behind.
Even more fascinating is what occurs in the bird world this time of year. During these late summer days, migratory birds have been feeding heavily, increasing their body weight sometimes by as much as 100 percent as they store fat and protein. They are able to eat more food because their digestive organs actually increase in size (those that do not feed during migration actually shrink.) The birds’ reproductive organs actually atrophy and shrink as hormone levels fall with decreasing daylight. Flight muscles, heart, and lungs also increase in size.
Flocks of birds, especially red-winged blackbirds, are flying about in extremely large groups. The first nighthawks have been spotted flying through the evening sky. Crows and blue jays can be seen migrating in flocks of up to 200 birds. Grackles and robins are moving through, flying fast and straight through the sky. Migrating birds of prey can be seen circling on thermals, large bubbles of warm air rising in the sky. Migrating flickers fly through in swooping flight and sun themselves on roadsides.
Adult loons begin flying south in late August and early September. Chicks stay on the nesting lakes, feeding and taking their first test flights, until nearly ice-over. One day, they start running across the water, take flight, and head south, where they will stay for the next three years. Most loon chicks will eventually return to their original nesting lake or find one nearby. Some loons do not establish their nesting territory until they are five years old.
We are beginning to see geese and some ducks flying in a regular V-shaped formation. One theory as to why they fly in this v-shape is that all birds except the one in the lead can gain lift from the wing-tip angles produced by the bird in front of them. According to scientists, the most efficient flight would include a one-fourth wingspan distance from the bird in front of it. However, motion pictures of flocks in flight show that Canada geese do not travel in these types of formations. Some scientists believe that the formations geese do use enable the birds to maintain visual contact and avoid possible mid-air collisions.
Become a phenologist! Keep your eyes open for migrating birds. Try counting them as they move through and track the date and numbers you observe. To get a good count, try counting as many as you can in a short time (before they are out of sight), and then estimate what fraction of the flock you have counted and multiply.
Nature Watch is brought to you by the Cable Natural History Museum. For 40 years, the Museum has served as a guide and mentor to generations of visitors and residents interested in learning to better appreciate and care for the extraordinary natural resources of the region. The Museum invites you to visit its facility in Cable at 43570 Kavanaugh Street or on the web at www.cablemuseum.org to learn more about exhibits and programs.
Thursday, August 16, 2007
Phenology
Nature Watch
August 16, 2007
By Susan Benson,
CNHM Director of Education
What do Carolus Linnaeus, Aldo Leopold, and Henry Thoreau have in common?
They all studied and recorded phenology, the practice of tracking changes in nature through the seasons. Like the farmers of old, some use phenology to make decisions on when to plant or harvest crops. By recording the annual date of the migrating red-winged blackbirds in my backyard, I know when to look for them each year. As a gardener I know when to begin looking for the first fall frost. I also can make unexpected observations—for example, watching the 13-lined ground squirrel in the yard being repeatedly hassled by the nearby hummingbird, simply for moving a few inches! Or perhaps while walking down the road, we might glance at a monarch depositing the last eggs of the season.
Noticing those small “bugs,” mostly black with red lines on their backs? If a boxelder tree is planted nearby, neighbors might be experiencing an explosion of boxelder bugs. These insect populations grow exponentially during years seven through ten of a ten-year cycle. This year is number eight. These bugs eat other plants as well, and seek shelter in protected places, such as cracks and crevices in walls, doors, windows, or foundations. They seem to favor south and west exposures.
The avian world is now free from the challenging parental duties of establishing nesting territories, singing, building nests, incubating eggs, and feeding growing chicks. Many adult migratory birds now are molting their breeding plumages. Molting occurs in response to a mixture of hormonal changes brought about by seasonal changes. Feathers take special care, but in spite of preening, dusting, bathing, or other feather care, the feathers still wear out. Older feathers loosen in the sockets (follicles) by the growth of new feathers. Feathers that need to migrate long distances wear more rapidly than those of resident birds.
Many ducks and grebes change their feathers all at once in a period lasting from two weeks to a month. New feathers are necessary to keep the birds’ flying ability intact and strong. Birds such as chickadees, hawks, woodpeckers, and hummingbirds only molt once a year, maintaining the same colors. Resident birds require more insulating feathers and their winter plumage may contain more than twice as many feathers as their summer plumage.
While enjoying the blooming goldenrod, watch for a round lump on the stems of many goldenrod plants. This lump is produced by the activity of the goldenrod gall fly, whose larvae will spend the winter well-hidden and surrounded by food within the goldenrod stem. During the summer the female adult fly lays an egg on the stem; the egg hatches and the larvae chews its way into the stem, where the movement irritates the plant, which responds by making extra thick layers of plant tissue around the larvae. In the fall, the larvae will form an exit tunnel that ends close to the outer stem, and then returns to the center for the winter. In spring it will pupate and later emerge in late May or early June.
Out for a walk in the woods? Asters are blooming, especially the large-leafed aster, a purple/blue flower known as the lumberjack’s friend—when in need, the leaves can be used as toilet paper. Daisy Fleabane, a small daisy-like flower, also is blooming. This plant is beneficial to bees, which collect the pollen or suck nectar; to beetles who feed on pollen; and to many other butterflies, flies, wasps, and plant bugs. Red maples have been showing some touches of color, possibly due to stress brought on by this year’s drought conditions.
Become a phenologist! Watch for the changing plumage of our migratory birds, or the V of a flock of geese. Look closely at a daisy fleabane to see what insects might be hanging about. Look for your own signs that fall may be approaching.
Nature Watch is brought to you by the Cable Natural History Museum. For 40 years, the Museum has served as a guide and mentor to generations of visitors and residents interested in learning to better appreciate and care for the extraordinary natural resources of the region. The Museum invites you to visit its facility in Cable at 43570 Kavanaugh Street or on the web at www.cablemuseum.org to learn more about exhibits and programs.
August 16, 2007
By Susan Benson,
CNHM Director of Education
What do Carolus Linnaeus, Aldo Leopold, and Henry Thoreau have in common?
They all studied and recorded phenology, the practice of tracking changes in nature through the seasons. Like the farmers of old, some use phenology to make decisions on when to plant or harvest crops. By recording the annual date of the migrating red-winged blackbirds in my backyard, I know when to look for them each year. As a gardener I know when to begin looking for the first fall frost. I also can make unexpected observations—for example, watching the 13-lined ground squirrel in the yard being repeatedly hassled by the nearby hummingbird, simply for moving a few inches! Or perhaps while walking down the road, we might glance at a monarch depositing the last eggs of the season.
Noticing those small “bugs,” mostly black with red lines on their backs? If a boxelder tree is planted nearby, neighbors might be experiencing an explosion of boxelder bugs. These insect populations grow exponentially during years seven through ten of a ten-year cycle. This year is number eight. These bugs eat other plants as well, and seek shelter in protected places, such as cracks and crevices in walls, doors, windows, or foundations. They seem to favor south and west exposures.
The avian world is now free from the challenging parental duties of establishing nesting territories, singing, building nests, incubating eggs, and feeding growing chicks. Many adult migratory birds now are molting their breeding plumages. Molting occurs in response to a mixture of hormonal changes brought about by seasonal changes. Feathers take special care, but in spite of preening, dusting, bathing, or other feather care, the feathers still wear out. Older feathers loosen in the sockets (follicles) by the growth of new feathers. Feathers that need to migrate long distances wear more rapidly than those of resident birds.
Many ducks and grebes change their feathers all at once in a period lasting from two weeks to a month. New feathers are necessary to keep the birds’ flying ability intact and strong. Birds such as chickadees, hawks, woodpeckers, and hummingbirds only molt once a year, maintaining the same colors. Resident birds require more insulating feathers and their winter plumage may contain more than twice as many feathers as their summer plumage.
While enjoying the blooming goldenrod, watch for a round lump on the stems of many goldenrod plants. This lump is produced by the activity of the goldenrod gall fly, whose larvae will spend the winter well-hidden and surrounded by food within the goldenrod stem. During the summer the female adult fly lays an egg on the stem; the egg hatches and the larvae chews its way into the stem, where the movement irritates the plant, which responds by making extra thick layers of plant tissue around the larvae. In the fall, the larvae will form an exit tunnel that ends close to the outer stem, and then returns to the center for the winter. In spring it will pupate and later emerge in late May or early June.
Out for a walk in the woods? Asters are blooming, especially the large-leafed aster, a purple/blue flower known as the lumberjack’s friend—when in need, the leaves can be used as toilet paper. Daisy Fleabane, a small daisy-like flower, also is blooming. This plant is beneficial to bees, which collect the pollen or suck nectar; to beetles who feed on pollen; and to many other butterflies, flies, wasps, and plant bugs. Red maples have been showing some touches of color, possibly due to stress brought on by this year’s drought conditions.
Become a phenologist! Watch for the changing plumage of our migratory birds, or the V of a flock of geese. Look closely at a daisy fleabane to see what insects might be hanging about. Look for your own signs that fall may be approaching.
Nature Watch is brought to you by the Cable Natural History Museum. For 40 years, the Museum has served as a guide and mentor to generations of visitors and residents interested in learning to better appreciate and care for the extraordinary natural resources of the region. The Museum invites you to visit its facility in Cable at 43570 Kavanaugh Street or on the web at www.cablemuseum.org to learn more about exhibits and programs.
Thursday, August 9, 2007
Things Happening in Summer
Nature Watch
August 9, 2007
By Susan Benson,
CNHM Director of Education
Can you believe this hot weather, again? Do we really have to go another day without rain? It is observing life’s cycles that makes life so interesting, and a great topic of conversation as well. As we look around in nature, we see other signs foretelling of other upcoming climatic events. The nests of the bald-faced hornet, the world’s best paper makers, are growing layer-by-layer seen as gray masses up in trees. Acorns will be falling from the trees to provide meals for black bears, wood ducks, deer, and turkeys. Believe it or not, some birds are already beginning to migrate south.
Some male ruby-throated hummingbirds begin migrating south as early as July, while the juvenile may not leave until November. Some warblers, shorebirds, and nighthawks have begun migrating south. Common grackles, red-winged blackbirds and geese are now gathering together in large flocks.
Keep an eye out for northern flickers along roadsides as they are foraging for ants. This bird species eats more ants than any other bird species in North America. Flickers are known for their behavior called “anting” in which flickers allow ants to crawl up on their wings. There are different theories as to why this happens: one is that the ants’ formic acid is used as a fungicide or insecticide against feather or skin parasites or fungus. Another speculation is that anting is a comfort activity that stimulates the skin during a summer molt.
If you have any fruit trees in your back yard, look for bird visitors to those trees. If you have a black cherry (Prunus serotina) there are at least 47 species who eat the fruit, including the northern flicker, rose-breasted grosbeak, and white-throated sparrow. Pin cherries attract eastern bluebirds along with many other bird species. Red elderberry fruit is fed on by scarlet tanagers, gray catbirds, American robins, and rose-breasted grosbeaks.
Jewelweed, which is blooming right now, has orange-yellow flowers which resemble miniature cornucopias, and hang from flexible stems. Researchers believe that the flexible stems could be a mechanism for hummingbird flower pollination. When the hummer feeds, the spring-like stem pulls the flower forward, putting pollen on the bird’s upper bill. Be sure to check back soon after jewelweed has finished blooming, because when the “touch-me-not” seeds have ripened, simply touching the bulging seed pod will bring about an exciting explosion almost quicker than the eye.
When finished finding the jewelweed in your nearest wet marshy area, be sure to put on the calendar the upcoming fantastic display of natural fireworks, the Perseid meteor shower. With a dark sky from the new moon on Sunday, August 12, there will be little moonlight, making this year’s meteor show a great one, possible one or two per minute during the shower’s peak. The show begins at 10:00 p.m. By 2:00 a.m. Monday morning it is possible that there might be dozens crossing the sky an hour. The source of this shower is Comet Swift-Tuttle, whose tail intersects Earth’s orbit every year in August. Tiny bits of comet dust hit our atmosphere making a vivid streak through the night sky.
Become a phenologist! Changes in sunlight are driving our seasonal changes, and plants and animals around the globe respond in a fascinating myriad of ways. Watch how our seasons affect the web of life. Get out an enjoy them – grab a chair and blanket and find the nearest field or clearing for the perseids, or hike through a nearby trail!
Nature Watch is brought to you by the Cable Natural History Museum. For 40 years, the Museum has served as a guide and mentor to generations of visitors and residents interested in learning to better appreciate and care for the extraordinary natural resources of the region. The Museum invites you to visit its facility in Cable at 43570 Kavanaugh Street or on the web at www.cablemuseum.org to learn more about exhibits and programs.
August 9, 2007
By Susan Benson,
CNHM Director of Education
Can you believe this hot weather, again? Do we really have to go another day without rain? It is observing life’s cycles that makes life so interesting, and a great topic of conversation as well. As we look around in nature, we see other signs foretelling of other upcoming climatic events. The nests of the bald-faced hornet, the world’s best paper makers, are growing layer-by-layer seen as gray masses up in trees. Acorns will be falling from the trees to provide meals for black bears, wood ducks, deer, and turkeys. Believe it or not, some birds are already beginning to migrate south.
Some male ruby-throated hummingbirds begin migrating south as early as July, while the juvenile may not leave until November. Some warblers, shorebirds, and nighthawks have begun migrating south. Common grackles, red-winged blackbirds and geese are now gathering together in large flocks.
Keep an eye out for northern flickers along roadsides as they are foraging for ants. This bird species eats more ants than any other bird species in North America. Flickers are known for their behavior called “anting” in which flickers allow ants to crawl up on their wings. There are different theories as to why this happens: one is that the ants’ formic acid is used as a fungicide or insecticide against feather or skin parasites or fungus. Another speculation is that anting is a comfort activity that stimulates the skin during a summer molt.
If you have any fruit trees in your back yard, look for bird visitors to those trees. If you have a black cherry (Prunus serotina) there are at least 47 species who eat the fruit, including the northern flicker, rose-breasted grosbeak, and white-throated sparrow. Pin cherries attract eastern bluebirds along with many other bird species. Red elderberry fruit is fed on by scarlet tanagers, gray catbirds, American robins, and rose-breasted grosbeaks.
Jewelweed, which is blooming right now, has orange-yellow flowers which resemble miniature cornucopias, and hang from flexible stems. Researchers believe that the flexible stems could be a mechanism for hummingbird flower pollination. When the hummer feeds, the spring-like stem pulls the flower forward, putting pollen on the bird’s upper bill. Be sure to check back soon after jewelweed has finished blooming, because when the “touch-me-not” seeds have ripened, simply touching the bulging seed pod will bring about an exciting explosion almost quicker than the eye.
When finished finding the jewelweed in your nearest wet marshy area, be sure to put on the calendar the upcoming fantastic display of natural fireworks, the Perseid meteor shower. With a dark sky from the new moon on Sunday, August 12, there will be little moonlight, making this year’s meteor show a great one, possible one or two per minute during the shower’s peak. The show begins at 10:00 p.m. By 2:00 a.m. Monday morning it is possible that there might be dozens crossing the sky an hour. The source of this shower is Comet Swift-Tuttle, whose tail intersects Earth’s orbit every year in August. Tiny bits of comet dust hit our atmosphere making a vivid streak through the night sky.
Become a phenologist! Changes in sunlight are driving our seasonal changes, and plants and animals around the globe respond in a fascinating myriad of ways. Watch how our seasons affect the web of life. Get out an enjoy them – grab a chair and blanket and find the nearest field or clearing for the perseids, or hike through a nearby trail!
Nature Watch is brought to you by the Cable Natural History Museum. For 40 years, the Museum has served as a guide and mentor to generations of visitors and residents interested in learning to better appreciate and care for the extraordinary natural resources of the region. The Museum invites you to visit its facility in Cable at 43570 Kavanaugh Street or on the web at www.cablemuseum.org to learn more about exhibits and programs.
Thursday, August 2, 2007
More Summer
Nature Watch
August 2, 2007
By Sue Benson,
CNHM Director of Education
Did you know that the first known written phenology records date back to 974 B.C. in China, or that the Japanese have records of the peak cherry blooms for the past 1,200 years? Phenology continues to provide joy to many people as they study the life cycles of plants and animals as they respond to seasonal changes.
Looking out towards the roadsides brings a splash of beautiful colors this time of year. If it is yellow that greets the eye, it could be early goldenrod or a number of other flowers. Goldenrod typically grows from knee- to waist-high, and can be identified by small yellow flowers located in pyramid-shaped clusters at the top the leafy stems. Tansy grows 3-4 feet tall, with heavily cut leaves, and a disc of smaller flowers that look like bright yellow buttons; this plant was brought from Europe because it was used in windows to keep flies away. Common mullein is a tall yellow spike with soft, hairy leaves at the base of the stem.
Shades of lavender also flash from the roadsides, and start with the very edge of the roads with short, fuzzy, fur-like flowers called rabbit’s foot clover, named for their resemblance to rabbits’ paws. Blazing stars are slender, spike-like plants that can grow up to 5 feet tall. They have grass-like leaves and hairy stems. Wild bergamot is lavender with firecracker-looking flowers and square, grooved stems, about 3 feet high. This plant is in the mint family and is used to make tea, is noted for its fragrance, and is used as an oil.
Joe-pye weed is a member of the aster family, and has purple flowers on the head and a purple spotted stem. This plant is often found in wet meadows or shallow marshes. Another lavender flower with a short tuft of flowers is spotted knapweed, an introduced, invasive species that can quickly take over fields and roadsides with its production of over 1000 seeds per plant.
Looking into the bird world this time of year, we will often find loon chicks diving and catching food on their own. Their wings are becoming more developed as they exercise them more. Adult loons will often leave the chicks and form pre-migratory flocks in early August. Mourning doves can be working on their third clutch of eggs for the season.
How do hot summer temperatures affect our waterways? According to Senior Fisheries Biologist Frank Pratt of the Hayward DNR, the Namekagon River currently is experiencing one-third less flow than average—the lowest on record. Surface temperatures for many area lakes are running 75-79 degrees F right now. Temperature data from a USGS gauge at Leonard's Spur in Hayward shows that on 90+ air temperature days, the water is at 67-69 F in early morning hours and rises to 77-80 F in late afternoon/early evening.
When air temperatures are in the mid-70s to mid-80s the water temperature cycle is more like 59-64 F at the low end and 74-78 F at the high end. Pratt stated, “For most species except trout, cisco, whitefish, and northern pike, these temps (70-80) are good for growth and survival. That’s why we call species like musky, bass, bluegill etc. "warm-water" species. The former group would be what we call "cold-water" or "cool-water" species. They seek out cooler water (<70) href="http://www.cablemuseum.org/">http://www.cablemuseum.org to learn more about exhibits and programs.
August 2, 2007
By Sue Benson,
CNHM Director of Education
Did you know that the first known written phenology records date back to 974 B.C. in China, or that the Japanese have records of the peak cherry blooms for the past 1,200 years? Phenology continues to provide joy to many people as they study the life cycles of plants and animals as they respond to seasonal changes.
Looking out towards the roadsides brings a splash of beautiful colors this time of year. If it is yellow that greets the eye, it could be early goldenrod or a number of other flowers. Goldenrod typically grows from knee- to waist-high, and can be identified by small yellow flowers located in pyramid-shaped clusters at the top the leafy stems. Tansy grows 3-4 feet tall, with heavily cut leaves, and a disc of smaller flowers that look like bright yellow buttons; this plant was brought from Europe because it was used in windows to keep flies away. Common mullein is a tall yellow spike with soft, hairy leaves at the base of the stem.
Shades of lavender also flash from the roadsides, and start with the very edge of the roads with short, fuzzy, fur-like flowers called rabbit’s foot clover, named for their resemblance to rabbits’ paws. Blazing stars are slender, spike-like plants that can grow up to 5 feet tall. They have grass-like leaves and hairy stems. Wild bergamot is lavender with firecracker-looking flowers and square, grooved stems, about 3 feet high. This plant is in the mint family and is used to make tea, is noted for its fragrance, and is used as an oil.
Joe-pye weed is a member of the aster family, and has purple flowers on the head and a purple spotted stem. This plant is often found in wet meadows or shallow marshes. Another lavender flower with a short tuft of flowers is spotted knapweed, an introduced, invasive species that can quickly take over fields and roadsides with its production of over 1000 seeds per plant.
Looking into the bird world this time of year, we will often find loon chicks diving and catching food on their own. Their wings are becoming more developed as they exercise them more. Adult loons will often leave the chicks and form pre-migratory flocks in early August. Mourning doves can be working on their third clutch of eggs for the season.
How do hot summer temperatures affect our waterways? According to Senior Fisheries Biologist Frank Pratt of the Hayward DNR, the Namekagon River currently is experiencing one-third less flow than average—the lowest on record. Surface temperatures for many area lakes are running 75-79 degrees F right now. Temperature data from a USGS gauge at Leonard's Spur in Hayward shows that on 90+ air temperature days, the water is at 67-69 F in early morning hours and rises to 77-80 F in late afternoon/early evening.
When air temperatures are in the mid-70s to mid-80s the water temperature cycle is more like 59-64 F at the low end and 74-78 F at the high end. Pratt stated, “For most species except trout, cisco, whitefish, and northern pike, these temps (70-80) are good for growth and survival. That’s why we call species like musky, bass, bluegill etc. "warm-water" species. The former group would be what we call "cold-water" or "cool-water" species. They seek out cooler water (<70) href="http://www.cablemuseum.org/">http://www.cablemuseum.org to learn more about exhibits and programs.
Wednesday, July 25, 2007
Summer
Nature Watch
July 25, 2007
By Sue Benson
Director of Education, Cable Natural History Museum
Keep your eyes out for the Eastern gray treefrog, a common species throughout Wisconsin. The population of these frogs has been increasing, possibly because of their ability to survive on the edge of human development. This treefrog prefers forested uplands near water to sustain good populations. Its scientific name, Hyla versicolor, is appropriate as its color varies depending on the temperature and surroundings, changing from bright green to gray with a range of mottled colors in between.
Sandhill crane chicks and young mallards have learned to fly in the past week. Crows have begun to flock together, and are often seen out in the fields, probably feasting on grasshoppers. Bird songs in the forest have decreased to almost nothing with the end of the nesting season. Keep your ears tuned for the few songs that remain – that of the veery (a resonating, ethereal descending song,) great-crested flycatcher (ascending wheep,) red-eyed vireos (Here I am, where are you? sounds), and the American robin.
Serviceberries and pin cherries should be peaking now. Sunflower, joe pye weed, spotted jewelweed, and goldenrod are in bloom. Goldenrods often have a “bad rap” for the onset of summer hay fever. These plants do produce pollen but in small quantities, heavy and sticky, attracting insects for pollination, but not carried on the wind. It is instead common ragweed that ushers in the hay fever season as this plant now begins to bloom. Although not recognized by most people, the tiny ragweed flowers produce huge quantities of very light pollen that is caught by the wind and can be carried for distances greater than 125 miles.
Common butterflies flitting about on blooming wildflowers include the white admirals, identified through their black wings with a broad white band; and fritillaries, a common group of butterflies of different sizes that can be seen in sunny meadows, with wings that are orange with broken black spots and occasional metallic silver marks.
Chipmunks begin collecting and storing seeds now through the end of October and can cache away as many as eight pounds of food to eat during the winter. Deer antler growth is nearing its peak. In the aquatic world, northern pike and muskellunge fingerlings are leaving the shelter of wetlands for open water.
For early risers, Mars and Mercury are both visible before sunrise in the eastern sky. For those who are late to bed, the Southern Delta Aquarid meteor shower peaks on July 28. The meteors can be seen over many nights before and after that date, so get outdoors to catch a shooting star. The second full moon of the month is July 29.
Become a phenologist! Begin recording the dates you observe the blooming of your favorite flowers, or the last day you hear the beautiful song of the veery in the forest in your backyard. Collect annual data that will allow you to create your own almanac so that you may notice how climate and weather play a major role in the life cycles of plants and animals.
Nature Watch is brought to you by the Cable Natural History Museum. For 40 years, the Museum has served as a guide and mentor to generations of visitors and residents interested in learning to better appreciate and care for the extraordinary natural resources of the region. The Museum invites you to visit its facility in Cable at 43570 Kavanaugh Street or on the web at http://www.cablemuseum.org/ to learn more about exhibits and programs.
July 25, 2007
By Sue Benson
Director of Education, Cable Natural History Museum
Keep your eyes out for the Eastern gray treefrog, a common species throughout Wisconsin. The population of these frogs has been increasing, possibly because of their ability to survive on the edge of human development. This treefrog prefers forested uplands near water to sustain good populations. Its scientific name, Hyla versicolor, is appropriate as its color varies depending on the temperature and surroundings, changing from bright green to gray with a range of mottled colors in between.
Sandhill crane chicks and young mallards have learned to fly in the past week. Crows have begun to flock together, and are often seen out in the fields, probably feasting on grasshoppers. Bird songs in the forest have decreased to almost nothing with the end of the nesting season. Keep your ears tuned for the few songs that remain – that of the veery (a resonating, ethereal descending song,) great-crested flycatcher (ascending wheep,) red-eyed vireos (Here I am, where are you? sounds), and the American robin.
Serviceberries and pin cherries should be peaking now. Sunflower, joe pye weed, spotted jewelweed, and goldenrod are in bloom. Goldenrods often have a “bad rap” for the onset of summer hay fever. These plants do produce pollen but in small quantities, heavy and sticky, attracting insects for pollination, but not carried on the wind. It is instead common ragweed that ushers in the hay fever season as this plant now begins to bloom. Although not recognized by most people, the tiny ragweed flowers produce huge quantities of very light pollen that is caught by the wind and can be carried for distances greater than 125 miles.
Common butterflies flitting about on blooming wildflowers include the white admirals, identified through their black wings with a broad white band; and fritillaries, a common group of butterflies of different sizes that can be seen in sunny meadows, with wings that are orange with broken black spots and occasional metallic silver marks.
Chipmunks begin collecting and storing seeds now through the end of October and can cache away as many as eight pounds of food to eat during the winter. Deer antler growth is nearing its peak. In the aquatic world, northern pike and muskellunge fingerlings are leaving the shelter of wetlands for open water.
For early risers, Mars and Mercury are both visible before sunrise in the eastern sky. For those who are late to bed, the Southern Delta Aquarid meteor shower peaks on July 28. The meteors can be seen over many nights before and after that date, so get outdoors to catch a shooting star. The second full moon of the month is July 29.
Become a phenologist! Begin recording the dates you observe the blooming of your favorite flowers, or the last day you hear the beautiful song of the veery in the forest in your backyard. Collect annual data that will allow you to create your own almanac so that you may notice how climate and weather play a major role in the life cycles of plants and animals.
Nature Watch is brought to you by the Cable Natural History Museum. For 40 years, the Museum has served as a guide and mentor to generations of visitors and residents interested in learning to better appreciate and care for the extraordinary natural resources of the region. The Museum invites you to visit its facility in Cable at 43570 Kavanaugh Street or on the web at http://www.cablemuseum.org/ to learn more about exhibits and programs.
Friday, July 20, 2007
Osprey
Nature Watch
July 20, 2007
By Sue Benson,
Director of Education, CNHM
Flight of the Fish Hawk
On a lazy summer day at your favorite lake or river, chances are good you’ll spot a bald eagle soaring high overhead or looking down from its perch on the upper branches of a big white pine. Thanks to cleaner waterways, habitat preservation, and federal and state protection, the once-rare eagle is now a common sight in the north woods.
While scanning the skies, though, you may be lucky enough to catch sight of another big raptor, one less common than the eagle but also found along rivers, lakes or wetlands. With a six-foot wingspan and a white head, the osprey might be mistaken for a bald eagle, though a closer look will reveal the bird’s distinguishing characteristics.
Perhaps most notable are the osprey’s wings, which look somewhat crooked because in flight they’re angled backward at the wrist. In contrast to the dark-bodied bald eagle, the underside of an osprey’s head, neck, chest, legs and wings are white; its tail is a mix of white and brown stripes.
Also known as the “fish hawk,” the osprey eats almost exclusively fish. The bird hovers over open water until it eyes its prey, then plunges downward feet first to grab the unsuspecting fish. Ospreys can’t swim, and occasionally drown when they latch on to a fish too large to lift from the water.
While bald eagles may spend the winter up north, ospreys migrate to warmer southern states in the fall and return to Wisconsin in mid-April to mate and nest. The nests are located near water and built on top of trees, power poles or human-made osprey nesting platforms. The nests themselves are usually more than three feet wide and are made of big sticks lined with grasses and weeds. During the month it takes for eggs to incubate, the female osprey rarely leaves the nest, while the male brings her fish to eat.
Though ospreys live on all continents except Antarctica, they have never been numerous in Wisconsin. In the 1950s, their modest population declined due to the harmful impacts of pesticides like DDT. Once these substances were banned in the early 1970s, osprey populations began to recover. In 1989 the osprey was reclassified from “endangered” to “threatened” in Wisconsin, but seeing these powerful, graceful birds remains a rare, exciting treat.
Brought to you by the Cable Natural History Museum. For 40 years, the Museum has served as a guide and mentor to generations of visitors and residents interested in learning to better appreciate and care for the extraordinary natural resources of the region. They invite you to visit their facility in Cable on 43570 Kavanaugh Street or at the website at http://www.cablemuseum.org/ to learn more about their exhibits and programs.
July 20, 2007
By Sue Benson,
Director of Education, CNHM
Flight of the Fish Hawk
On a lazy summer day at your favorite lake or river, chances are good you’ll spot a bald eagle soaring high overhead or looking down from its perch on the upper branches of a big white pine. Thanks to cleaner waterways, habitat preservation, and federal and state protection, the once-rare eagle is now a common sight in the north woods.
While scanning the skies, though, you may be lucky enough to catch sight of another big raptor, one less common than the eagle but also found along rivers, lakes or wetlands. With a six-foot wingspan and a white head, the osprey might be mistaken for a bald eagle, though a closer look will reveal the bird’s distinguishing characteristics.
Perhaps most notable are the osprey’s wings, which look somewhat crooked because in flight they’re angled backward at the wrist. In contrast to the dark-bodied bald eagle, the underside of an osprey’s head, neck, chest, legs and wings are white; its tail is a mix of white and brown stripes.
Also known as the “fish hawk,” the osprey eats almost exclusively fish. The bird hovers over open water until it eyes its prey, then plunges downward feet first to grab the unsuspecting fish. Ospreys can’t swim, and occasionally drown when they latch on to a fish too large to lift from the water.
While bald eagles may spend the winter up north, ospreys migrate to warmer southern states in the fall and return to Wisconsin in mid-April to mate and nest. The nests are located near water and built on top of trees, power poles or human-made osprey nesting platforms. The nests themselves are usually more than three feet wide and are made of big sticks lined with grasses and weeds. During the month it takes for eggs to incubate, the female osprey rarely leaves the nest, while the male brings her fish to eat.
Though ospreys live on all continents except Antarctica, they have never been numerous in Wisconsin. In the 1950s, their modest population declined due to the harmful impacts of pesticides like DDT. Once these substances were banned in the early 1970s, osprey populations began to recover. In 1989 the osprey was reclassified from “endangered” to “threatened” in Wisconsin, but seeing these powerful, graceful birds remains a rare, exciting treat.
Brought to you by the Cable Natural History Museum. For 40 years, the Museum has served as a guide and mentor to generations of visitors and residents interested in learning to better appreciate and care for the extraordinary natural resources of the region. They invite you to visit their facility in Cable on 43570 Kavanaugh Street or at the website at http://www.cablemuseum.org/ to learn more about their exhibits and programs.
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