Nature Watch
October 8, 2008
By Susan Benson,
CNHM Director of Education
Every autumn we revel in the beauty of the fall colors. The mixture of red, purple, orange and yellow is the result of chemical processes that take place in the tree as the seasons change from summer to winter. During the spring and summer the leaves have served as factories where most of the foods necessary for the tree's growth are manufactured. This foodmaking process takes place in the leaf in numerous cells containing chlorophyll, which gives the leaf its green color. This extraordinary chemical absorbs from sunlight the energy that is used in transforming carbon dioxide and water to carbohydrates, such as sugars and starch. Along with the green pigment are yellow to orange pigments, carotenes and xanthophyll pigments which, for example, give the orange color to a carrot. Most of the year these colors are masked by great amounts of green coloring.
Chlorophyll Breaks Down
In the fall, because of changes in the length of daylight and changes in temperature, the leaves stop their foodmaking process. The chlorophyll breaks down, the green color disappears, and the yellow to orange colors become visible and give the leaves part of their fall splendor.
At the same time other chemical changes may occur, which form additional colors through the development of red anthocyanin pigments. Some mixtures give rise to the reddish and purplish fall colors of trees such as dogwoods and sumacs, while others give the sugar maple its brilliant orange.
The autumn foliage of some trees show only yellow colors. Others, like many oaks, display mostly browns. All these colors are due to the mixing of varying amounts of the chlorophyll residue and other pigments in the leaf during the fall season.
Other Changes Take Place
As the fall colors appear, other changes are taking place. At the point where the stem of the leaf is attached to the tree, a special layer of cells develops and gradually severs the tissues that support the leaf. At the same time, the tree seals the cut, so that when the leaf is finally blown off by the wind or falls from its own weight, it leaves behind a leaf sear. Most of the broad-leaved trees in the North shed their leaves in the fall. However, the dead brown leaves of the oaks and a few other species may stay on the tree until growth starts again in the spring. In the South, where the winters are mild, some of the broad-leaved trees are evergreen; the leaves stay on the trees during winter and keep their green color.
Weather Affects Color Intensity
Temperature, light, and water supply have an influence on the degree and the duration of fall color. Low temperatures above freezing will favor anthocyanin formation producing bright reds in maples. However, early frost will weaken the brilliant red color. Rainy and/or overcast days tend to increase the intensity of fall colors. The best time to enjoy the autumn color would be on a clear, dry, and cool (not freezing) day.
Enjoy the color; it only occurs for a brief period each fall.
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 13470 County Highway M or on the web at http://www.cablemuseum.org/ to learn more about exhibits and programs.
Wednesday, October 8, 2008
Wednesday, October 1, 2008
Fall Trees & Birds
Nature Watch
October 2008
By Susan Benson,
CNHM Director of Education
Are the pines dying? When did the hummers last leave the feeders? These are some of the questions that have filtered into the Museum in the last two weeks. Read on for more answers.
Using the term “evergreen” to describe our conifers is not quite right. It is normal for some needles on our area’s conifers to fall off the trees. This occurrence, called fall needle drop, is a loss of the oldest and innermost needles shed from our pines, spruce and fir. Some fear that this is a disease, insect, or other warning sign, but is natural this time of year. Pines shed their oldest needles in the fall, and white pines usually shed their needles every two years. Sometimes the needle drop occurs in a short period of time, rapidly browning and falling, and other years, it’s almost unnoticeable because the discoloration happens over a longer time period. Environmental stress conditions can also affect this event, as root stress from extended dry periods, excess soil moisture, or poorly drained soils can impact this phenomenon, creating a greater needle loss. By the end of the needle drop, the trees may look bare, having lost approximately a third of their needles, and if the current season’s needle growth was a good one, there can be a greater fall needle drop. The needles on the tips of the branches are the newest growth, and if they were brown, this would be a larger concern and indication that something might be wrong with a particular tree.
What is happening in the bird world? Yellow-rumped warblers and sparrows are still migrating through. Migrating raptors and geese are still observable as is the occasional thrush in the forest. The ruby-throated hummingbirds appear to be gone. As requested in a previous article, last day reports came into the Museum from several people: September 16, September, 13, September 13, September 15 - all observed in the Cable area. Another report from Cable shared the past three year’s data: 2006, September 9; 2007, September 8; 2008, September 13. Thanks to those who shared this information! Ruby-throats do not do well in temperatures below the mid-20s (F), so this, mixed with the photo-period (shortening day length,) sends them south. A larger contributing factor driving migration is when there is the greatest food abundance. Banding studies have shown that those we saw in mid-September were not necessarily the same individuals we saw throughout the summer. Stumpy and the others we may have named at our feeders (this name comes from one of the Cable bird reports) might already be gone. The number of birds migrating south could be double that of the spring migration with the addition of immature birds. The immature have no memory of past migrations, and so follow an urge to gain weight and fly; once their flight is established the first time, it is possible that this becomes the route that bird retraces throughout its life. Some recommendations for those of us who have hummingbird feeders are to keep them out two weeks past the last day sighted, just in case there is a later migrant looking for food. At the same time, it is suggested to not keep your feeders out in conditions where they might freeze.
Earlier in the week it was raining pine needles. Today the sun shines. Our glorious fall weather and events continue. Get outdoors and enjoy it more, and please email any unusual observations to info@cablemuseum.org.
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 13470 County Highway M or on the web at http://www.cablemuseum.org/ to learn more about exhibits and programs.
October 2008
By Susan Benson,
CNHM Director of Education
Are the pines dying? When did the hummers last leave the feeders? These are some of the questions that have filtered into the Museum in the last two weeks. Read on for more answers.
Using the term “evergreen” to describe our conifers is not quite right. It is normal for some needles on our area’s conifers to fall off the trees. This occurrence, called fall needle drop, is a loss of the oldest and innermost needles shed from our pines, spruce and fir. Some fear that this is a disease, insect, or other warning sign, but is natural this time of year. Pines shed their oldest needles in the fall, and white pines usually shed their needles every two years. Sometimes the needle drop occurs in a short period of time, rapidly browning and falling, and other years, it’s almost unnoticeable because the discoloration happens over a longer time period. Environmental stress conditions can also affect this event, as root stress from extended dry periods, excess soil moisture, or poorly drained soils can impact this phenomenon, creating a greater needle loss. By the end of the needle drop, the trees may look bare, having lost approximately a third of their needles, and if the current season’s needle growth was a good one, there can be a greater fall needle drop. The needles on the tips of the branches are the newest growth, and if they were brown, this would be a larger concern and indication that something might be wrong with a particular tree.
What is happening in the bird world? Yellow-rumped warblers and sparrows are still migrating through. Migrating raptors and geese are still observable as is the occasional thrush in the forest. The ruby-throated hummingbirds appear to be gone. As requested in a previous article, last day reports came into the Museum from several people: September 16, September, 13, September 13, September 15 - all observed in the Cable area. Another report from Cable shared the past three year’s data: 2006, September 9; 2007, September 8; 2008, September 13. Thanks to those who shared this information! Ruby-throats do not do well in temperatures below the mid-20s (F), so this, mixed with the photo-period (shortening day length,) sends them south. A larger contributing factor driving migration is when there is the greatest food abundance. Banding studies have shown that those we saw in mid-September were not necessarily the same individuals we saw throughout the summer. Stumpy and the others we may have named at our feeders (this name comes from one of the Cable bird reports) might already be gone. The number of birds migrating south could be double that of the spring migration with the addition of immature birds. The immature have no memory of past migrations, and so follow an urge to gain weight and fly; once their flight is established the first time, it is possible that this becomes the route that bird retraces throughout its life. Some recommendations for those of us who have hummingbird feeders are to keep them out two weeks past the last day sighted, just in case there is a later migrant looking for food. At the same time, it is suggested to not keep your feeders out in conditions where they might freeze.
Earlier in the week it was raining pine needles. Today the sun shines. Our glorious fall weather and events continue. Get outdoors and enjoy it more, and please email any unusual observations to info@cablemuseum.org.
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 13470 County Highway M or on the web at http://www.cablemuseum.org/ to learn more about exhibits and programs.
Day in October
Nature Watch
October 15, 2008
By Susan Benson,
CNHM Director of Education
What do birds do on a rainy, overcast day in October? I found out this weekend on a bike ride. Almost every day this fall I have gotten outdoors on my bike for a ride along the Namakagon River. Last Sunday, the maples were at peak. This week the aspens were at peak. Today, the maple I’ve watched change colors daily, was barren of every single leaf. Each day I stop along the route some place to make new observations. During this week’s bike ride, I watched and heard two bald eagles, an adult and juvenile calling; heard their wing beats above my head; and watched the adult fly swiftly and impressively as it followed along the Riverway. Slate-colored juncos were madly darting after each other through the brush. Black-capped chickadees and white-breasted nuthatches were flitting about. White-throated sparrows and many warblers were also foraging along the river.
Earlier in the week I was astounded by the numbers of migrating robins. They were everywhere, flying through the river valley, but in many other places around the region as well. I stopped long enough to find their favorite places, and discovered a chokecherry tree that had been almost completely stripped of all berries – in its upper branches the fruit stalks were empty. It was evidence that as our ground chills in the fall, robins do adapt their diet away from earthworms and more towards berries.
Robins form loose flocks for both feeding and flying during migration. By traveling in greater numbers, they are more able to notice predators and warn the others. Another advantage of their large flocks is that some individuals who have more experience and familiarity with an area can show others feeding or roosting areas. Their migration is patchy, with individuals spread throughout a bigger range to ensure that they will not deplete available food sources. Robins migrate mostly during the day, although move occasionally at night. They can fly up to 36 miles per hour, so can accomplish up to 200 miles per day. Robins often move ahead of warm fronts, arriving just before or along with rainy weather. Mixing these high pressure systems with northwesterly winds are good conditions for migration.
Migrate yourself outdoors this coming week, and enjoy all that fall still has to offer!
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 new facility in Cable at 13470 County Highway M or on the web at http://www.cablemuseum.org/ to learn more about exhibits and programs.
October 15, 2008
By Susan Benson,
CNHM Director of Education
What do birds do on a rainy, overcast day in October? I found out this weekend on a bike ride. Almost every day this fall I have gotten outdoors on my bike for a ride along the Namakagon River. Last Sunday, the maples were at peak. This week the aspens were at peak. Today, the maple I’ve watched change colors daily, was barren of every single leaf. Each day I stop along the route some place to make new observations. During this week’s bike ride, I watched and heard two bald eagles, an adult and juvenile calling; heard their wing beats above my head; and watched the adult fly swiftly and impressively as it followed along the Riverway. Slate-colored juncos were madly darting after each other through the brush. Black-capped chickadees and white-breasted nuthatches were flitting about. White-throated sparrows and many warblers were also foraging along the river.
Earlier in the week I was astounded by the numbers of migrating robins. They were everywhere, flying through the river valley, but in many other places around the region as well. I stopped long enough to find their favorite places, and discovered a chokecherry tree that had been almost completely stripped of all berries – in its upper branches the fruit stalks were empty. It was evidence that as our ground chills in the fall, robins do adapt their diet away from earthworms and more towards berries.
Robins form loose flocks for both feeding and flying during migration. By traveling in greater numbers, they are more able to notice predators and warn the others. Another advantage of their large flocks is that some individuals who have more experience and familiarity with an area can show others feeding or roosting areas. Their migration is patchy, with individuals spread throughout a bigger range to ensure that they will not deplete available food sources. Robins migrate mostly during the day, although move occasionally at night. They can fly up to 36 miles per hour, so can accomplish up to 200 miles per day. Robins often move ahead of warm fronts, arriving just before or along with rainy weather. Mixing these high pressure systems with northwesterly winds are good conditions for migration.
Migrate yourself outdoors this coming week, and enjoy all that fall still has to offer!
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 new facility in Cable at 13470 County Highway M or on the web at http://www.cablemuseum.org/ to learn more about exhibits and programs.
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