Monday, April 26, 2010

Woodcock Sky Dance

By Susan Benson,
CNHM Director of Education

It was later in the evening, about a week ago that I was out hooting for a barred owl response. Lately, the barred owls have been frustratingly elusive. However, this particular evening, I heard a sound of another bird that was exciting to hear. The American woodcock was “peenting.” “It was doing what,” you say? Some look funny at me when I say the word. No, “peenting” is not a dirty word. Peenting is sound made by the woodcock during its elaborate courtship display that the male uses to attract females. What a show the male woodcocks provide!

First, the woodcock begins his song and dance at sunset, in a field or clearing. He sings out, calling repeated “peents,” followed by an occasional bobbing or curtsy of his head, a turn, and a repeat of the dance again while broadcasting his song in different directions. After a few bobs and peents, he flies upward into the sky in a wide spiral, moving higher and higher. As he gets higher, his wings whistle, creating a “twittering” sound. How is the twitter made? As air passes between the first primary feathers on his wing, it produces a whistling sound. As the woodcock gets to a height of 200-300 feet, he begins to chirp. The vocal chirping sound marks the descent downward, where he spirals or zig-zags back and forth, diving quickly down to the ground without a sound. Just as the chirping stops is when a look just above the horizon can show him flying in for a landing. When he lands, he often settles in at almost the exact same spot, with hopes that a female is nearby. Then he starts the entire dance again. The display goes on sometimes for at least an hour past sunset, or on moonlit nights, even longer.

The male American Woodcock does not provide care for its young, but continues the display even after females have laid their eggs. Some males will use different song and dance grounds, mating with several females.

It was Aldo Leopold who named the woodcock spring rituals the Sky Dance, as anyone can read in his Sand County Almanac. I learned first about the song and dance while waiting for its flight dance. Once it left off into the air, I would sneak up closer until I was just a few feet away in the dusk light. I watched with delight as it sang and danced. There is magic in experiencing the woodcock dance, and is a spring ritual not just for the woodcock, but for birders like me to enjoy. Try it on your own some night soon. Seat yourself under a bush just off the dance floor and wait, watching against the sunset for the woodcock’s arrival. Once finished watching the display, then curl up on the couch with a copy of Leopold’s book to relive the magic once again.

For over 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 and new exhibit, On Lake Owen: The Art of Walter Bohl, in Cable at 13470 County Highway M. Also find us on the web at www.cablemuseum.org to learn more about our exhibits and programs. Post your own stories on the Nature Watch blog at cablemuseumnaturewatch.blogspot.com.

Friday, April 23, 2010

Bird Migration

By Susan Benson,
CNHM Director of Education

What causes the push for bird migration? With an early spring, do the birds return early? Food and reproduction are the two most critical factors in migration. The changing seasons cause decreases in a bird’s food supply, causing birds to move to an area with more plentiful food availability. With a greater density of birds in the southern areas during our winters, food supply gets shorter, causing a push to move to another area where greater food supplies exist. A second factor is that birds also migrate to an area to raise their young. What are the internal and external cues that lead to this bi-annual migration for so many birds?

A major cue for bird migration is the change in day length, or photoperiod. These changes cause different hormone levels in birds that affect metabolism and the drive to reproduce. As daylight lengthens, there is a change in the lower part of the brain, the hypothalamus, that controls hunger and causes birds to gain weight through overeating, leading to as much as a forty percent weight gain. These fat deposits are stored in the bird’s flight muscles, under their skin, and in their abdominal area. Birds maintain this weight gain metabolism throughout their migratory activity. As daylight changes, other hormonal changes in birds lead to a display of higher activity, or restlessness in birds, especially at night.

Hormonal changes also bring a drive for reproduction. Spring migration becomes an urgent time for birds, as there is an optimal time for birds to arrive in their breeding areas. Stronger males arrive first to stake out the best nesting habitats. When females arrive, they select the prime areas in which to raise their young. For example, the house wren males arrive first into the northwoods habitats. They will begin building up to twelve different nest sites. Although they weight the equivalent of two quarters, the males will harass other larger birds, even taking eggs or young out of a nest site they want. When the female arrives, she chooses what she believes will be the most successful nest, and that male becomes her mate. Younger males will learn from their elders, usually choosing to nest near the older males, gaining knowledge of the best nesting habitats.

It is believed that day length is not the only factor that stimulates the drive to migrate. Temperature also plays a part. When spring is late, birds do not arrive early, and when spring is early, the birds can move in earlier to take advantage of the best natural resources. Scientists also believe that vegetative cover can influence light levels to impact reproduction.

Although there can be variability from year to year, scientists do believe that long-term averages show a trend that, in the last 20 years, birds are arriving earlier, and a larger number of species are shifting farther north in search of food. The theory is that climate change could be disrupting some birds’ migratory patterns.

Is there any time better than spring (besides, summer, autumn, and winter, of course?) Right now, spring rules our world, bringing us opportunities for observing birds in their bright plumage, or outdoor concerts as the males sing, declaring their territory. Spring is so sweet!

For over 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 and new exhibit, Our Shared Planet, in Cable at 13470 County Highway M. Also find us on the web at www.cablemuseum.org to learn more about our exhibits and programs. Post your own stories on the Nature Watch blog at cablemuseumnaturewatch.blogspot.com.

What dates have the American robins return? The following dates were reported by Museum members:

1995 3/16

1996 3/21

1997 3/21

1998 3/23

1999 3/11

2000 3/15

2001 3/18

2002 3/26

2003 3/26

2004 3/22

2005 3/22

2007 3/21

2009 3/15

2010 3/18

Monday, April 12, 2010

Salamanders

By Susan Benson,
CNHM Director of Education

With the forecast of a possible rain, it is difficult not to get excited, since it seems like a long time since we have seen precipitation in our area. One of the events I will be looking forward to is an event that happens yearly after the ground has thawed and the weather warms up. Salamanders are often on the move during the first warm, hard, night rain. Salamanders are amphibians not as well known as the spring peepers or other frogs because they are very secretive. In order to see one, it helps to be outdoors at night, as they are a mostly nocturnal animal. In Wisconsin, we have seven species of salamanders, whose cold-blooded body temperatures reflect their environments. They prefer night as they can take advantage of cooler, more humid conditions that keep their skin from drying out. They are most easily seen in spring and fall as they migrate to and from their breeding wetlands. With enticing names like newts, mole salamanders, lungless salamanders or mudpuppies, who could not want to learn more?

Where are salamanders in the spring? As soon as the edge of the ice is open, salamanders move from their terrestrial hiding places into their wetland habitats, usually ephemeral ponds (ponds that have been temporarily created by snowmelt and spring rains,) or in wetlands that do not support fish, major predators of salamander eggs and larvae. Breeding activity occurs when water temperatures are 50 to 60 degrees Fahrenheit. The spotted salamander breeds in large groups, while others breed in single pairs. The females often guard their eggs and secrete slime to prevent fungal growth or other destruction. Once hatched, the larvae fall into the pond where they develop until their final metamorphosis. The red-backed salamanders are an exception, being entirely terrestrial, looking for moist habitats to lay their eggs. The unique central newt can produce an aquatic adult, a terrestrial eft (juvenile) and a terrestrial adult.

Salamanders have some other interesting characteristics. Mole salamanders, commonly named the blue-spotted, tiger, and spotted salamanders, exude a defensive, sticky secretion that is foul-tasting to predators. They spend most of their time underground and eat a variety of invertebrates including insects, earthworms, mollusks, and even young rodents. These species can also sometimes be found under rotting logs. The central newt is primarily aquatic, yet also has toxic skin to protect itself. Newts eat earthworms, aquatic insects, snails, and other amphibian larvae. The lungless salamanders have four toes on their hind feet, while other species have five. The red-backed salamander is one of the most abundant species in Wisconsin, commonly found under rotting logs. Mudpuppies are exclusively aquatic, living in lakes and rivers with preferred large, flat rock habitats.

Like other reptiles and amphibians, salamanders shed their skin occasionally, often eating their skin sheds for the nutrients. Some salamanders protect their vital organs by arching their back downward, throwing back their head, and extending their tail over their back. Some salamanders will wag their tails or wiggle their bodies to distract a predator from attacking their heads. For some salamanders, their tails, when grasped, can break off and later partially regenerate. Salamanders also are able to re-grow toes or limbs, or even regenerate their eye tissue.

Salamanders are important for a variety of reasons. The red-backed salamander alone is thought to number in thousands per acre, making their sheer biomass important as a food source to mammals, birds, fish, or reptiles. They are also a predator of many insects or other invertebrates in aquatic or terrestrial environments. They are indicators of local environmental quality, as their permeable skin is vulnerable to pollutants. Maybe most importantly, for many children, one of their first experiences outdoors could be with a frog or salamander. Since my first experience looking for salamanders, I have never looked at a rotting log quite the same. Salamanders are worth carefully searching for as they are beautiful creatures.

For over 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 and new exhibit, Our Shared Planet, in Cable at 13470 County Highway M. Also find us on the web at www.cablemuseum.org to learn more about our exhibits and programs. Post your own stories on the Nature Watch blog at cablemuseumnaturewatch.blogspot.com.

Monday, April 5, 2010

Mourning Cloaks

By Susan Benson,
CNHM Director of Education

The sun is shining, and the last of the melting snow trickles down the driveway. Fluttering down past me goes the first butterfly of the season. A butterfly, in March or April? The main coloration of this butterfly is dark purple-brown, with yellow edges on its wings. Its underside is mottled gray with a lighter yellow edging. It flies straight, flapping alternating with sailing as it moves along by us. This butterfly is a mourning cloak, and it is one of nature and spring’s first happy signs!

Mourning cloaks are named for their dark coloring, which resembles the traditional mourning cloak worn when someone is mourning. In truth, its dark colors warm it faster on the sunny spring days, allowing it to move about when most insects are still not capable of movement. They get warmed up through basking in the sunlight, as they need body temperatures close to that of humans in order to fly. Once they begin their flight their muscles provide enough heat to keep them going. This is passive solar heating at its finest.

Why are mourning cloaks the first spring butterflies? They overwinter as adults, having spent the winter in cryo-preservation. In the fall, mourning cloaks produce antifreeze proteins that they circulate through their blood. These proteins bind to the surface of tiny ice crystals to prevent them from growing bigger and harming the tissues. They also build up higher concentration of sugars, called glycerol, in their blood and tissues to lower the freezing point of their body. Finally, they hide in tree cavities, beneath tree bark, or under leaf litter. It is important, however, that they find a fairly dry place to overwinter so they can avoid contact with ice in the environment that surrounds them. This adult strategy is a different form of hibernation to be sure!

During the spring and summer, the adult mourning cloaks feed on tree sap, especially from oak trees, or fermenting fruit. Occasionally mourning cloaks will be seen at sapsucker holes feeding on sap, or at mud puddles or animal scat where they extract nutrients. When females lay their up to 250 eggs, they prefer willow, birch, aspen, or elm trees. The eggs hatch within about ten days, and the caterpillars are black with red and white spots, with bristly spines on their body. The larvae feed together in silk webs in their large family groups. If they overfeed and wipe out the food supply on the tree, they will move along single file in a line to the next feeding site. By mid-June they leave their host plants, and go off in search of a new site, where they pupate for about 10-15 days. They are believed to be one of the longest-living butterflies, living up to ten months as adults.

With these amazing early spring temperatures, be sure to get outdoors and enjoy the warm weather. Keep your eyes open for a chance encounter with this lovely butterfly. Perhaps you will be lucky and it will fly or land right near you.

For over 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 and new exhibit, Our Shared Planet, in Cable at 13470 County Highway M. Also find us on the web at www.cablemuseum.org to learn more about our exhibits and programs. Post your own stories on the Nature Watch blog at cablemuseumnaturewatch.blogspot.com.