The life story of a vulture.

News and commentary about environmental issues.
Feb. 2 2009 7:21 AM

Vulture World

From a continuing series on revolting creatures.

More revolting creatures: the tick and the jellyfish.

Vulture.
A vulture

A few weeks ago, I spent a surprisingly pleasant morning watching vultures in the "Birds of Prey" section of the Bronx Zoo in New York City. The birds, juvenile females named Patsy and Dolly, were calm and curious, dropping down to the front of the cage every time someone stopped. When lunch came, they used their big, flat feet to steady packages of recently thawed rat carcasses as they undid them with their hooked bills. (Zookeepers wrap the dead rats in paper, tightly tied with string, to make the dining process more interesting.) A point of contention with the zoo categorization of Patsy and Dolly: They aren't really birds of prey—they're birds of clean-up.

The eagles and hawks we admire, the real predators, tear their living victims apart. Vulture meals involve no frenzied chase or bloody kill—in fact, no haste or suffering at all. Vultures wait a couple of days till the spirit of the deceased has safely departed and gases begin to leak from the decomposing corpse.

It's unfair that this avian clean-up crew excites dread and disgust. School kids at the zoo that morning ran from the two vultures shrieking, "Ewww, gross." I refrained from reasoning with the little screamers: Would you rather have putrefying carcasses or nice, clean bones lying around?

Some visitors even stone the poor vultures, according to a zoo curator. Unjust though this is, it's understandable that we find the carrion-eating birds gruesome. Most of us would rather not think of ourselves as meat, and the details of vulture dining are hard to get comfortable with. Vultures, whose name comes from vellere, Latin for to tear, begin their eating at vulnerable spots on the carcass—the anus and eyes.

Patsy and Dolly are king vultures, close cousins to the bald, red-wrinkle-headed turkey vulture that plies the skies from southern Canada to the bottom tip of South America. It's the turkey vulture we're most likely to see on the wing or on the carcass.

The distinctive red head on males and females is probably attractive to a potential mate, explains William Lynch, president of the Turkey Vulture Society. The society, 91 members strong, is a sort of vulture anti-defamation league set up to fight misconceptions and encourage appreciation. (According to an FAQ on their Web site: No, under the terms of the Migratory Bird Treaty Act of 1918, you cannot keep a turkey vulture as a pet. You can attract them to your yard, however, if you're willing to cart home some roadkill. Tupperware is recommended.)

Lynch goes on to say that vulture baldness means not having to preen feathers after dipping into a bloody carcass. The society members write appreciatively about the turkey vulture's impressive 6-foot wingspan, its brownish-black plumage, and particularly its ruff of soft feathers with a purple sheen.

Turkey vulture advocates want us to know that the birds do not circle over dying things; the implication of the common cartoon image of vultures above the crawling man in the desert is slanderous, says Lynch. The birds circle as they ascend on thermals—columns of warm rising air. If, as choreographers say, grace is the elimination of extraneous movements, their flight is graceful. They ride air currents for hours with no flapping. They rock and sway, ranging over dozens of square miles, returning to roost sociably with their fellows in late afternoon.

It is not surprising to learn that vultures do not sing to one another with pretty songs. No warble or trill. Bird behavior books mention only three sounds: hisses, grunts, and a hoarse rattle. Lynch believes he's discovered a fourth vocalization—a kind of discreet cough, between ack and ahem—made by a parent upon returning to the nest. He hopes to publish his observations in an upcoming issue of Vulture News.

As they ride the wind, vultures seek dead things, not dying things, using a sense of smell far more highly developed than any other bird's. They can detect a dead mouse under leaves from 200 feet up. They are discriminating, preferring corpses between two and four days dead. (The turkey vulture entry in the definitive Birds of North America Online does note, "Takes live prey occasionally in unnatural situations.")

Another misconception, and one that has caused farmers to shoot them, is that turkey vultures spread disease. In fact the opposite is true. Something in the vulture gut allows them to digest and destroy the agents of diseases such as cholera and anthrax. If another carrion-eater—rat or coyote or hyena or dog—disposed of the infected carcass, contamination would be spread.

To those who prefer not to have vultures pooping on their building ledges or roofs or decks, Lynch says, "Their waste is as clean as any waste can be." But there is some threat to human beings from the other end of the vulture digestive system. If adults are threatened when nesting, they throw up on the intruder or play dead. (The latter seems a poor strategic choice, given their companions.)

Vulture nestlings are also armed with vomit—but the downy-white chicks with sheeplike black faces are still vulnerable to raccoons, skunks, fox, and possums. After successfully repelling a threat, the vulture, ever a model of conservation, re-eats the spit-up food.

Under threatening circumstances, an angry bird can aim green vomit at you from as far away as six feet. Normally, though, a turkey vulture's sociability extends to human beings as well as to its fellows.  The people who care for injured wild birds report that vultures are gentle, inquisitive, and smarter than hawks and eagles. Here's the bottom line, from Lynch: "Once they get to know you they don't regurgitate on you."

Like morticians, these dealers in death also die. In the wild, vultures live about 10 years. If death doesn't occur because of old age, it comes from starvation, electrocution at power lines, trapping, shooting, ingestion of lead from animals that have been shot, or getting run over by a car. (A turkey vulture, ungainly on land, has a hard time getting airborne quickly, a serious problem if it's working on road kill.)

What would happen without them? The major vulture news of the last decade gives a clue. A mysterious die-off of Asian white-backed vultures has led to a pileup of domestic animal carcasses and an increase in the population of rodents and feral dogs. It turned out that an anti-inflammatory drug—diclofenac—used on sick livestock kills vultures even in low doses. Though the Indian government is phasing out the veterinary use of the drug, the vulture population hasn't rebounded. One social consequence has been that members of the Zoroastrian Parsi community, who have used vultures to dispose of human corpses, now have to cremate their dead. But that doesn't solve the problem of animal carcasses in a vulture-free world. Let's be grateful the turkey vultures are keeping us from being awash in dead raccoons.

* * *

More revolting creatures: the tick and the jellyfish.

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