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Birds on the Move

Winter 2002-2003 Newsletter

The melancholy sight of Canada geese heading south signals that winter is on its way.

Migrating birds may travel thousands of miles to Central or South America or simply move a few hundred miles south or from a higher elevation to a lower one for the colder months.

Not all birds migrate. Many species — those that feed on seeds, dried fruit, and rodents — reside year-round here in Northwest Illinois.

Migrating birds must build up their body weight before beginning their journeys. That’s why we see the Ruby-throated Hummingbird (Archilochus colubris) constantly at our feeders in August and September.

These tiny birds, measuring only 3 1/2 inches, fly down to Mexico and Central America. The Arctic Tern (Sterna paradisaea) makes one of the longest migrating flights.

Hormonal changes and the shortening of days signal birds that it is time to migrate. Most stop along the way, but when they reach a large body of water, they must cross nonstop. The birds may become so exhausted when they reach the shore that they literally fall from the sky. Some never reach land and perish.

Birds may follow specific flyways such as the Mississippi River or a seacoast, or migrate across a broad area. They orient themselves by the earth’s physical features and the stars and sun. Scientists believe that the earth’s magnetic field might also help them find their way.

Some species migrate at heights of up to 20,000 feet, where thinner air and cooler temperatures conserve their energy.

No, it’s not true that hummingbirds hitch a ride on the backs of geese. They make their long trip south all by themselves.