Urban animal study finds that NYC, Boston pigeons don’t mix
Almost 1 in 5 Americans lives in the megacity that is the Northeast, a sprawling cluster of paved surfaces, bitter sports rivalries and clashing opinions about which city’s drivers are rudest.
Each city on the road up Interstate 95 from Washington to Boston prides itself on its uniqueness. But it turns out that parts of the animal world have their own senses of geography.
At the genomic level, a new study finds, most of the Eastern Seaboard’s pigeons are all mixed up. That means those birds shuffling through Central Park, clucking on the National Mall, hanging out in Baltimore’s Inner Harbor or getting chased down a Philadelphia back alley by Gritty? All one interconnected population, denizens of an unbroken avian super-metropolis.
Except New England pigeons, that is, which seem to keep to themselves.
After Elizabeth Carlen, a biologist at Fordham University, caught pigeons with a net gun and took their blood samples during a series of road trips across the region, she discovered that birds all the way from Virginia to southern Connecticut show genetic signs of interbreeding. And in a paper published this month in Evolutionary Applications, she and a co-author also report that another separate, distinct pigeon supercity begins in Providence, Rhode Island, and continues to Boston.
“That was really weird to think about,” Carlen said.
The suburbs of Connecticut don’t just mark the boundary between Yankees and Red Sox fans, or tomatobased and cream chowders: They also seem to block pigeons. Discovering two distinct pigeon megalopolises was a surprise to Carlen.
“My original hypothesis was that each city was going to be a separate population,” she said.
Previous studies had shown that pigeons are homebodies, staying within hundreds of feet of where they were born.
But it’s possible that all it takes is one intrepid pigeon finding an out-of-town mate every generation to explain how cities like Baltimore, Washington, Philadelphia and New York can have so many genetic similarities, she said.
Less than 200 miles separate New York and Boston, but something between the rival towns forms an uncrossable moat for cityslicker pigeons. A look at satellite maps of artificial light at night highlights the gap between the two metropolitan areas — a break in what is otherwise continuous urban sprawl. Although the birds can fly, all that rural green space might dissuade them from attempting a crossing.
The result adds to the growing field of urban evolution, the study of how wildlife changes in and around some of the least natural environments on the planet.