Some of Georgia’s migratory birds — shorebirds, ruby-throated hummingbirds, orchard orioles and others — began heading south in late July and early August. Many of them already are ensconced in their winter homes in Central and South America.
But for most of Georgia’s migratory birds, including some 50 species of songbirds that nested here during spring and summer, fall migration revs up this month. It will peak in late September and early October.
Here’s a brief primer:
Q: How do birds know when it’s time to head south?
A: Probably a number of things tell them it’s time to leave — cooler temperatures, changes in food supplies, natural instinct. The biggest cue, however, is changing day length. After the summer solstice on June 21, days become shorter. Birds are extremely sensitive to such change.
Q: How do first-year migratory songbirds — those that hatched during spring — learn how to migrate for the first time in fall?
A: Research shows that young birds are born with an amazing innate map — their own GPS — which gives them direction and distance to travel during migration. This is evident from the many young birds, such as warblers, thrushes and vireos, that make their very first migration on their own in fall, without their parents. Somehow they can find their winter home despite never having seen it before, and return the following spring to where they were born.
Q: What routes do birds take when migrating in the fall to Latin America?
A: Birds navigate along more or less regular routes when they migrate. In North America, these “avian superhighways” include the Atlantic, Mississippi, Central and Pacific flyways. In Georgia, migratory birds generally travel the Atlantic Flyway. The route starts in Greenland, then follows the Atlantic coast of Canada, then south down the U.S. Atlantic Coast to the tropics of South America and the Caribbean. Many of the migrating birds rely on specific habitats along the flyway, such as coastal marshes, forests and grasslands, for resting and refueling.
IN THE SKY: From David Dundee, Tellus Science Museum astronomer: The moon will be new on Thursday. Venus is low in the east just before dawn. Mars is very low in the west at dark. Jupiter is in the south at dark. Saturn rises in the east before sunset and is up nearly all night.
Charles Seabrook can be reached at charles.seabrook@yahoo.com.
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