No matter how urbanized New Yorkers like to think we are, the reminders of our natural world are constant. Canada geese, raccoons even skunks have brushed up against humans recently in a somewhat rude manner. Or at least it was rude to us.
But as the temperatures drop ever so slowly, there above us in the autumn skies are thousands of migrating birds, and except for the geese and swooping flocks in the sky, they pass without giving us much notice of their transit. They usually fly at night, over the heads of sleeping urbanites. Often, the flocks leave behind casualties of the lit skyscrapers, although New York City Audubon is working to change that.
Like truckers on their CB radios, these birds call to each other, and each species has its own migratory call. Andrew Farnsworth, who studies bird migration at Cornell University, has been recording these calls as the birds wend their way across the city.
“You have to be a pretty astute observer to even know that it happens,” Dr. Farnsworth said.
Dr. Farnsworth puts microphones on the roofs of buildings around the city, although the only one that consistently will be posted this fall is the recorder on his building on First Avenue. The majority of the calls have been recorded at night, and most of the calls are less than one-third of a second long. Even asleep, the city roars like a rushing river. But if you listen carefully …
“You have to have a pretty good ear, too,” Dr. Farnsworth said.
The study of night migration calls is a significant but small part of migration studies, Dr. Farnsworth said, although recording night calls themselves is not new. It is challenging, though, in part because the calls are so short. The Cornell Lab of Ornithology has a deep repository of samplings of bird calls, and Mr. Farnsworth and his colleagues have developed a “Rosetta stone” for identifying 48 different species.
Alan Clark, a biologist at Fordham University who also works with migration calls, said this year his program in the Bronx added radar, which gives researchers a better sense of how many birds are in the air. But the sounds themselves can also help ornithologists determine how many birds migrate and when, and how conditions in the city affect the birds’ flight, he said.
The bird calls are the highest notes of the city’s fall song, and we’ve included some to satisfy your curiosity. These aren’t the typical warbles you hear on a sunny fall afternoon; they’re short, very quiet and muffled by the roar of the city below.
A wood thrush, whose brethren have been migrating across New York City at night.
http://cityroom.blogs.nytimes.com/2010/09/09/above-the-city-at-night-the-call-of-the-wild-is-heard/ Night bird calls here on right
