Vultures Take Over Suburbia
They vomit all over the place, urinate on themselves to cool off, and feed on the dead. Now they're disgusting and even frightening suburban homeowners. But vultures are amazing creatures that are a key part of the food chain, and they reveal a lot about wildlife's ability to adapt to us.
"Here they come!" The shout goes out from the far side of a tulip poplar, in the backyard of a slate-roofed house in the historic district of Leesburg, Virginia, about 40 miles northwest of Washington, D.C. I look up. About a half-mile away, black specks pepper the horizon. At first it's difficult to identify the birds. They are tiny, coal-colored filaments, like a child's stick-figure drawings of gulls in flight, adrift in a reddening sky. But after a brief few seconds, this becomes evident: The birds are large. They are numerous. And they are flying straight toward us.
In fact, those birds--mostly black vultures, with a smattering of their red-headed kin, turkey vultures--know exactly where they want to be: roosted for the night in one of the trees beside the big fieldstone house at 212 Cornwall Street. They've been here for weeks. At first just a few dozen settled each sunset into a pair of tall pines. Evening by evening, more joined the roost. Their numbers climbed to 100, then 200, then 300. They filled the pines until boughs sheared off with their collective weight. The roost trees were slathered in excrement, white as candles. On sunny mornings the birds warmed their wings on the house's rooftop. On cooler days they skulked on the gravestones of a small cemetery next door, sliming the markers with chalky feces. Now the acrid scent of their waste wafts down the street. And Leesburg has had enough.
Dage Blixt, a biologist with the U.S. Department of Agriculture's Animal and Plant Health Inspection Service (APHIS), points a small pistol skyward. He is a soft-spoken man with close-cropped hair and round wire-rimmed glasses, and he leads the five-person roost-dispersal squad hailed to Leesburg by town officials. A trio of black vultures arrows overhead, bold and muscular in flight. Blixt pulls the trigger and a 15mm Screamer Siren pyrotechnic shell corkscrews into the darkening sky, trailing orange sparks, screeching like a car with locked brakes. The shell narrowly misses a dead vulture, trussed by the feet and hoisted 40 feet into a pine. (Such tactics discourage vultures from a roost site.) The black vultures tuck and roll, surprisingly agile for their size. They circle overhead, confused. But there's no peace to be found. The air is filled with screamer shells and Bird Banger rounds, another pyrotechnic that explodes with a loud report up to about 100 yards in the air. Vultures that do find purchase in the roost trees are "shot" with the beam of a red laser that can reach 800 feet. The light is harmless, but it spooks the birds, and that's the point.
This is the first of 10 nights of vulture hazing in the streets of Leesburg, but it is just a tiny skirmish in a protracted struggle to deal with growing populations of these birds across much of eastern America. Of the three species of New World vultures occurring in the Lower 48 (one of which is the critically endangered California condor), black vultures and turkey vultures are doing a fine job of bouncing back from DDT contamination and heavy persecution in the early 20th century, when ranchers and farmers shot them by the tens of thousands. An increase in deer populations--and a corresponding spike in roadkill and carcasses during hunting seasons--plays a part, too.
Most often it's the black vultures that are, quite literally, pissing off their human neighbors, but these birds are more valuable than they're given credit for. "Vultures are one of the better disease control mechanisms out there," says Christopher Brand, research chief for the USGS National Wildlife Health Center, in Madison, Wisconsin. "They check the flow of infectious wildlife diseases such as botulism and possibly anthrax." (These birds evolved with the ability to metabolize natural biotoxins found in decaying flesh.) And given the way vultures use their sense of smell, they can find carcasses that go undetected by other scavengers, such as opossums, crows, and magpies.
What's more, it's hard to fathom what American roadsides would look like without vulture cleanup crews. A bird on the carcass is better than a few thousand maggots and untold bacteria, reasons Greg Butcher, Audubon's director of bird conservation. "We tend to like the other things that clean up carcasses even less."
Trouble is (from the disgusted-human perspective), black vultures are exploiting urbanizing landscapes, thanks to an increase in food sources such as roadkill and, from all indications, a warmer environment provided by growing acres of asphalt and concrete. In fact, the same things that draw new human residents to a burgeoning area are high on a vulture's relocation wish list: Great roads. Warm climate. Lots of open space but still convenient to good shopping.
If scientists can tease apart the causes of their success, it could help us learn to fashion a world where other living creatures can overcome an ever bigger human footprint. "The attitude is they are too ugly and too common for most people to appreciate. But we don't know enough about these birds," says Keith Bildstein, director of conservation science for Pennsylvania's Hawk Mountain Sanctuary. "We need to understand the biology of successful species, because what makes one species successful can help us better understand those that are really struggling to remain a part of our world."