A Fat Bird is a Happy Bird

November 20, 2007

WCS ornithologists are discovering that New York City is bug heaven for hungry songbirds passing through on their way to northern breeding and southern wintering grounds.

New York is an eater’s town, a place where people are proud to be “chowhounds” and eating like a bird is, well, for the birds. But that’s good enough for white-throated sparrows and hermit thrushes, among other migratory songbirds passing through the city on the Atlantic flyway. Hungry for insects, worms, and berries to fuel their journeys south toward the Caribbean in winter, and north toward Canada in spring, the birds make pit stops along their way to regain the 10 or 15 percent of their body mass they can lose during a typical night’s tiresome commute.

Awaiting the birds as they touch down on Bronx Zoo grounds are Wildlife Conservation Society (WCS) researchers Chad Seewagen and Eric Slayton. The ornithologists are studying the migrants to determine whether they are able to get their fill of bird food in New York’s crucial stopover points—those nutritious green spaces that are few and far between, from a bird’s-eye-view.

To conduct their analysis, Chad and Eric have strung up mist nets along the Bronx River to snare the migrants for a brief exam. The researchers carry them to their mobile physiology laboratory, provided by the University of Western Ontario, where they measure and weigh the birds, take blood samples, and band them. As the final step, the birds get a mini-MRI exam, which estimates fat content, their chief energy source. After the painless procedure, the birds take off to fit in another meal or two before they move on.

Chad and Eric’s New York Bird Monitoring Program will continue in the spring, when their study subjects return to the city along their northbound route. Preliminary results suggest the Bronx Zoo is indeed satisfactory dining turf from a Neotropical migrant’s perspective. The researchers are now expanding their work to nearby city and suburban parks. They have also begun presenting the research to local schoolchildren, to whom a city bird is generally one of two things: a pigeon or a starling.

“Most of the kids we’ve met are surprised that wild birds fly through their local parks,” Chad explained. “But a bright-colored warbler and other tropical-looking birds can be found right in the middle of New York City.” Even though most urbanites know that birds fly south for winter, it’s much harder to fathom that those birds pass right over their heads—and their high-rises. “Some of these birds who stop to eat in the Bronx might be headed to Puerto Rico,” Chad added. “That’s exciting to a kid whose family is from the island. It’s an instant connection to wild nature.”

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