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.
As natural land cover is replaced by parking lots, asphalt, and buildings, air and surface temperatures rise. The U.S. Environmental Protection Agency reports that many urban areas have air temperatures up to 10 degrees Fahrenheit warmer than the surrounding region. This so-called "urban heat island effect" is helpful to birds that require rising columns of heated air to locate food. "There is actually a new, manufactured thermal corridor that extends from Washington, D.C., to Philadelphia and on to New York," says Bildstein. "Warmer urban areas create thermals, and there is no question that soaring birds are using them to great effect."
Global warming may well be bringing them north, too. Black vultures soar higher than their turkey kin, and they tend to feed on larger prey. As overall temperatures inch upward, so does the thermal boundary at which carrion freezes, which makes it unusable to avian scavengers.
The National Park Service's Leslie has doubts: "We need to be very careful with linking climate change to the population change. There are so many other factors, including changes in the prey base [from more plentiful roadkill, for one example], that have enabled black vultures to expand northward."
But others are far more convinced. "Climatic change is the most important factor affecting black vulture range changes," says The Peregrine Fund's Lloyd F. Kiff. "This is a species where there is a direct correlation to temperature. The northern range limit is set by a thermal line that allows carcasses to stay unfrozen. And vultures are like people: They are going to take advantage of every opportunity presented to them."
Their spectral silhouettes catch my eye late one morning as I'm driving down a four-lane highway through the rolling Virginia piedmont. I switch on my hazard blinkers, pull off the shoulder, and grab binoculars as the car shudders from the turbulence of passing trucks.
Fifty yards away, two dozen black vultures and a handful of turkey vultures work over a large catfish carcass that they've dragged about 40 feet from the edge of a small pond. For the moment an older, gray-headed bird has control of the fish. He holds it with his left foot and sinks his bill deep into the entrails. As his head disappears inside the carcass, like an ostrich sticking its head in the sand, other black vultures hop in to snip a piece of fish flesh.
I watch for maybe 15 minutes. At one point the turkey vultures, shut out from the feast, take a few hops and wing off for prey they don't have to share. Now the king of the rotting catfish stands on one leg and uses a claw of the other to pick a piece of fetid meat from its nostril.
In the soft-focused background of my binoculars, 100 yards distant over a grassy field, red, white, and blue flags flap cheerfully in a stiff breeze: "Welcome!" they read. "Models Open!"
Roads are coming. Trees are falling. Another chunk of Virginia vanishes. More asphalt. More landfills. More roadkill. More vultures. After all, we laid out the welcome mat.
Watching that greedy vulture clean his nostrils while paring the catfish down to its skeletal essentials, I offer a silent resolution: Should these innocuous, if putrid, transplants ever come toting their trashy belongings onto my street, I'll be resolved to stand upwind and offer a neighborly wave of respect.
State of the Bird
Looks: Bulky body, short tail, broad wings, wingspan of about five feet. Plumage all black except for white flash near wingtips; head is featherless and dark gray.
Behavior: Feeds mainly on carrion, which it finds mostly by sight. Soars for hours, scanning for carcasses and watching the actions of other scavengers. Sociable, usually roosting in groups.
Range and habitat: From southern South America north through Central America and Mexico to southern Arizona and throughout the southeastern United States. Expanding range northward; now common to Ohio and Connecticut. Occupies all kinds of open and semi-open country.
Status: Christmas Bird Counts and Breeding Bird Surveys show steadily increasing populations in some areas in recent decades.
Threats: Growing vulture populations and spreading suburban sprawl are bringing vultures and humans into more contact and conflict.
Outlook: Long-term prospects may depend on educating the public about the important ecological role of scavengers.--Kenn Kaufman