Songbird Migration a Hemispheric-scale Phenomenon

In a single day in mid-spring as many as two million birds end their nonstop journey over the Gulf of Mexico by alighting in the trees and shrubs of coastal Louisiana and neighboring gulf shore states. “The birds look like a gigantic cloud stretching from Galveston to Vermilion Bay,” says Wylie Barrow, a wildlife biologist at the National Wetlands Research Center. Exhausted and hungry after the long flight, the birds tumble from the sky in a “fall-out.” The woody vegetation of cheniers, ridges and barrier islands provides food and shelter where the birds rest and replenish their stores of energy before flying on to summer destinations across the continent.

Using Doppler radar Barrow and his research team track the birds’ distribution and movement across the landscape. What he learns helps to shape practices for restoring and managing the habitat that songbirds depend on in their semiannual migration. In one project Barrow combines his data with satellite imagery to show how birds interact with various kinds, sizes and densities of vegetative cover. “We’re locating gaps of tens or hundreds of miles between patches of forest,” Barrow says. “We’re discovering how small an area can provide useful habitat. And we’re examining conditions within that habitat, looking at issues such as invasive plants’ influence on the availability of insects and other sources of nutrition.

“Because the greatest number of birds end their trans-gulf migration here each spring, the Chenier Plain plays a pivotal role in songbirds’ survival,” says Barrow. “Now we need to translate this awareness of the area’s importance into conservation actions, protecting and restoring the remnant forests of the gulf coast.”