Migrations-Sep. 2002

Comings and Goings

Migration in fall is more leisurely than in spring. There is no pressure of territory, displays and nesting. Birds can take their time making a move to a more Southern exposure. Remember, not all birds migrate; in fact, most don’t. Scientists estimate that only fifteen percent of all bird species seasonally change their homes. Scientists aren’t quite sure why birds migrate. One guess is that the yearly move has to do with bird comfort. The migrators are looking for warmer weather and better food. Others claim that migrating birds are heading back to their ancestral homes.

There is much mystery lore attached to the annual disappearance of the birds. Some thoughts are that birds hibernate in winter, huddling together at the bottom of ponds. One seventeenth century writer claimed birds spent their winters on the moon. Aristotle, the ancient Greek philosopher, believed that birds didn’t go anywhere but simply changed their identity with another species.

North American birds generally find their way south along one of four major “flyways”– which are bird versions of interstate highways. The most popular of these is the Mississippi River Flyway, which runs along the river and is easy to spot from the air. Other flyways run along the Atlantic and Pacific coasts, and down the Rocky Mountains.

So how do these marvels of nature manage to find their way in night skies? Some use landmarks such as, rivers and mountains as guideposts. Others pick up directional clues from the stars, and sun, or from earth’s magnetic field.

As August runs into September we can begin our watch for our traveling friends. Day skies and night skies are both equally used by the traveling troops of Aves. If you choose the right viewing spot, you can see spectacular flights of migrating hawks. At Hawk Mountain Sanctuary on the Kittatinny Ridge, near Harrisburg, Pa., for example, fights of 15,000 to 21,000 hawks have been observed on a single autumn day.

Like all birds, hawks need to conserve energy during migration, so they fly with the wind when possible or seek out thermal updrafts on which they can soar. When hawks find a wall or column of rising air, hundreds of soaring birds may collect in what are called kettles, and can be seen spiraling upward. These columns can be caused by wind blowing against the sides of mountains or by updrafts of hot air rising from the shorelines.

So don’t delay, find your ideal spot for spotting birds either in preflight preparation or during their annual flight. Some birds prepare for migration by adding on up to 50 percent of their body weight, so fall is a great time for bird watching. Call the Audubon connection at Beechwood Farms Nature Reserve for some ideal places to begin your birding activities.

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