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.