The black-and-white warbler
We are in the midst of spring migration, that special time of year when many bird species return from their wintering grounds to breed in the U.S. and Canada. A group of birds known as warblers virtually define migration for the birdwatcher. Highly active and often brightly colored, most warblers pass through Pittsburgh in waves, primarily in May and October each year.
One species winging its way to Pittsburgh is the pocket-sized black-and-white warbler. Just 41/2 inches long and boldly striped in black and white, this neotropical migrant flies thousands of miles from the Caribbean islands, Central America and northern South America to the forests of eastern North America to breed. It makes the return trip in fall, seeking reliable food and shelter throughout the winter.
As if such a long journey was not remarkable enough, this amazing bird is able to find its way back, year after year, to the very same breeding or wintering site that it occupied the previous year! In studies completed by me, the National Aviary ornithologist, individually marked black-and-white warblers returned to overwintering sites in the Dominican Republic that were no larger than a typical city lot in Pittsburgh.
During spring and summer, the black-and-white warbler is fairly common in Pittsburgh forests. It can be seen creeping along tree trunks and branches, always moving, turning back and forth, and circling over and under branches in search of insect prey. It also probes into crevices and hollows in the bark of the tree for hidden bugs.
The bird is considered "area sensitive" on its breeding grounds. It shies away from forests that have been subdivided or fragmented into smaller forest blocks. This happens when humans introduce housing, roadways, pipelines or other development into a forested landscape. Scientists are noting declines in populations of black-and-white warblers, and forest fragmentation may be the cause.
But with a collaborator from the U.S. Forest Service, Joseph Wunderle, we found that black-and-white warblers overwintering in the Dominican Republic were just as likely to live in small forest fragments as they were in larger forests. Such a finding supports studies that suggest that many migratory birds are more flexible in their habitat needs on the wintering grounds than they are on the breeding grounds where their habitat requirements for successful breeding may be very specific.
Don't miss out on the beauty of the season. Take some time to step out into our forests to scan the trees. You may find the unmistakable stripes of the black-and-white warbler, or another remarkable migratory traveler. Now is the time to enjoy these beautiful birds and wonder at their life journeys.
On May 11-12, the National Aviary will host Migration Celebration, a weekend devoted to the millions of birds who fly from the tropics to the U.S. and Canada in spring, only to return south a few months later. You can learn about their journeys, the challenges they face and what you can do here in Pittsburgh to help these birds thrive. More information at www.aviary.org.science