The Fall Migration is in Full Thrilling Flight
by Timothy Boucher
Fall migration literally brings birds of a different feather than in springtime. Spring migration brings a glorious burst of song and color as millions of tiny feathered gems pour northward, singing their hearts out, flitting about with the excitement of arrival at their breeding grounds. They are relatively easy to spot and identify by their voices and bright plumage.
In the fall, birdwatching is trickier. To survive, migrating birds need to go to warmer climes for food, because insects do not thrive in cold temperatures. Males molt their bright plumage, needing fresh feathers for the long flight. Most retain some color, but generally, they are duller and look similar to the females. Identification becomes harder because some species are similar in appearance and the singing gives way to an occasional, subtle call, emitted as little chipping sounds at most.
The Internet offers a comprehensive range of data that can suggest which days are best for early morning viewings. Experienced birders know the best local spots, and weather forecasts are good indicators of timing. Sid Gautreaux’s pioneering study of bird migration in the 1960s using weather radar, still ongoing at the Radar Ornithology Lab at Clemson University, is available to birders on regional websites via Tinyurl.com/USBirdTrackingRadar.
While radar can confirm the magnitude and direction of the migration over the previous night, weather predictions help forecast when big flights will occur. So, the next step is to hold a wetted finger up to the wind. A big cold front will hold up birds from moving south because the associated low pressure brings southerly winds and storms. Birds wait it out, storing fuel. Then, when the front clears and a tailwind comes from the north, a floodtide of birds pours southward.
Eager birders, having arrived shortly after dawn, await at selected spots 200 to 300 miles south of the leading edge of the former front. On days like these, the skies are brimming with birds. Grassroots monitoring reports on the birds’ progress from mid-August through October are posted at eBird.org, sponsored by New York’s Cornell Lab of Ornithology (Birds.Cornell.edu).
As Joni Mitchell sang, we rejoice that, “They’ve got the urge for going now, and they’ve got the wings to go.”
Timothy Boucher is a senior conservation geographer at The Nature Conservancy (Nature.org), focused on ecosystem services, land use, habitat conditions and links between conservation and human well-being. His fieldwork spans six continents, encompassing local and global issues.