vulture

Vultures are large birds who feed almost exclusively on carrion. They are divided into two groups, the New World (North and South America) and Old World (Africa, Europe and Asia) species. These two groups are only peripherally related in a taxonomic sense, and the similarity between the species is a result of convergent evolution. They are, for the most part, not nearing extinction but have suffered some significant setbacks as a result of direct or indirect human interference.

General biology and behaviour

Vultures are large, normally drab-coloured birds. The largest species is the Cinereous vulture, with a wingspan of 8 1/2 feet, while the smallest is the Hooded vulture which is roughly the size of a crow.

Almost all vultures are carrion specialists, the the notable exception of the Palm-nut vulture (Gypohierax angolensis) which feeds principally on the fruit of the oil palm. They are birds of prey, like falcons, eagles and hawks, but unlike the other members of the order (Falconiformes), have weakend feet and bills and thus are generally unable to prey upon living creatures (a notable exception is the American black vulture (Coragyps atratus) which is an agressive bird known for attacking small animals and even horses or cattle). The New World (North and South America) vultures are different from their Old World partners in nearly every way except for their appearance and behaviour (they occupy the same ecological niche).

Even among carrion-eaters, there is a strong hierarchy. When a carcass is located by a group of vultures, all the other birds in the region flock quickly to the scene. How they communicate their find (inadvertantly, surely), is unknown. The largest vultures (eg. King vultures) normally get the first crack at a carcass, and often have the opportunity to gorge themselves on the viscera, while the smaller species (eg. Black and turkey vultures) must consume the smaller pieces of muscle, tendon and ligaments that remain.

Vultures are wonderfully adapted to their feeding strategy. They have naked heads and necks, allowing the bird to fully insert its head into a carcass with a reduced risk of dirtying their bodies and allowing parasites to colonize. Further, after eating they will often bask in the sun, allowing whatever material remaining stuck to their heads or necks to bake, and thus kill any potential pathogens or parasites. Their relatively weak claws (as compared to a hawk or falcon; you still wouldn't want a vulture to grab your arm) are used to hold the carcass steady and the head and neck are inserted into the body cavity. The beak of a vulture is normally not sufficiently strong to kill an animal, but is more than capable of dismembering a carcass and picking the bones nearly clean. Some vultures even crack open bones in order to feed on the marrow inside. They feed in groups, and are such efficient eaters that smaller carcasses can be skeletonized within an hour.

Vultures have other adaptations as a result of their feeding strategy. They have very low metabolic rates, and can easily go days without any food. Given the intermittent nature of their food supplies, vultures can spend up to several days waiting on their roost for a feeding opportunity. They also have evolved wonderful abilities to neutralize the toxins in their rancid food. In fact, in one laboratory experiment, a captive bird was injected with enough botulinus toxin to kill 300 000 guinea pigs. The bird was fine, and in fact showed no symptoms.

Birds do not have the ability to sweat, so vultures had to find an alternative manner to thermoregulate (almost all vultures live in arid, hot climates). The vultures urinate on their own legs, allowing evapotranspiration to wick heat away from their bodies. As an added benefit, they have such strong and chemically potent urine that it will kill any bacteria or parasite clinging to the birds feet.

Vultures are not preyed upon by other creatures to a large extent, due to their size, impressive flying ability and their anti-predator defense. If threatened by an animal, most vultures will projectile vomit their stomach contents either on or near the predator. While that may sound sufficiently disgusting in and of itself, consider that they often consume rancid, maggot-ridden meat. Apparently, this vomit is the closest natural imitation of the putrid stench of Dante's Inferno that you can imagine.

Vultures play important roles in their ecosystems. They recycle many nutrients by consuming animal carcasses, and compete directly with pest insects for food. They are, in a sense, the caretakers of the bird world, cleaning natural habitats of dead animals at a remarkable rate.

Vultures are not known for impressive courtship displays, unlike many other bird species. Vultures are not exclusive when it comes to mating, like some birds, but may choose a different mate every year after sexual maturity. They construct nests in tress or on cliffs using twigs and branches. Most species produce only one chick per year, but both parents hunt and feed the chick by regurgitating their meals.

Conservation status

Most vulture species are not threatened or endangered (some are severly limited like the Cinereous vulture), but the species does suffer from a negative reputation among humans. They are shot on sight in some places in Africa (vultures are believed to carry disease), and many species are very badly impacted by human pollution. They are particularly succeptible to pesticides and other toxins, given their feeding habit (dead animals are often so because they have been poisoned) and bioaccumulation. The classic example of the devastation of the California Condor by the use of DDT in the 1950s and 1960s is another example of how humans can negatively affect these wonderful birds. And, as usual, they are often threatened by habitat destruction¹.

In recent years, some concern for certain species (most notably the King vulture and the Turkey vulture) has been raised by both homeowners and conservationists due to the propensity of vultures to become pests in urban settings. Due to their detritivorous lifestyle, they can survive quite well in cities by raiding dumps and relying on roadkill for sustenance. The size of the birds and their social nature (they can flock in groups of up to 70 animals) can make them a hazard to humans. And, given some of their aforementioned adaptations (see urination as thermoregulation and bacterial control and projectile vomiting) they certainly don't beautify the landscape very much. ssd has informed me that in Orlando, Florida, there are some resident populations which cease to migrate, and tend to roost on the justice building, overlooking the lawyers (coinkydink?)

Taxonomy

New World vultures
Order: Ciconiiformes²
Family: Ciconiidae (synonym: Cathartidae)
Genera, species:
Cathartes aura -- Turkey vulture
C. burrovianus -- Lesser yellow-headed vulture
C. melambrotus -- Greater yellow-headed vulture

Coragyps atratus -- American black vulture

Gymnogyps californianus -- Californian condor

Sarcorhampus papa -- King vulture

Vultur gryphus -- Andean condor


Old World vultures
Order: Falconiformes
Family: Accipitridae
Subfamily: Aegypiinae
Genera, species:
Aegypius calvus -- Red-headed vulture
A. monachus -- Cinereous (Black) vulture
A. occipitalis -- White-headed vulture
A. tracheliotus -- Lappet-faced vulture

Gypaetus barbatus -- Bearded vulture

Gypohierax angolensis -- Palm-nut vulture

Gyps africanus -- African white-backed vulture
G. bengalensis -- Indian white-backed vulture
G. coprotheres -- Cape vulture
G. fulvus -- Griffon vulture
G. himalayensis -- Hymalayan griffon
G. indicus -- Long-billed griffon
G. rueppelli -- Ruppell's vulture

Neocrosyrtes monachus -- Hooded vulture

Neophron percnopterus -- Egyptian vulture

Sarcoramphus papa -- King vulture


¹ Man, when you start writing a bunch of nodes about animals, this sure does become a tiresome and frightening refrain.
² New World vultures are tentatively placed in this order. Older classifications had them with the Falconiformes, like their Old World cousins, but new research suggests (based on genetic evidence) that they are in fact closer to storks and herons and should be moved to this order.

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Information culled from the following sources:
* http://www.accutek.com/vulture/biology.htm
* http://www.accutek.com/vulture/facts.htm
* http://www.vultures.homestead.com/about.html

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First published in AlienSkin Magazine, March 2008

Vul"ture (?; 135), n. [OE. vultur, L. vultur: cf. OF. voltour, F. vautour.] Zool.

Any one of numerous species of rapacious birds belonging to Vultur, Cathartes, Catharista, and various other genera of the family Vulturidae.

⇒ In most of the species the head and neck are naked or nearly so. They feed chiefly on carrion. The condor, king vulture, turkey buzzard, and black vulture (Catharista atrata) are well known American species. The griffin, lammergeir, and Pharaoh's chicken, or Egyptian vulture, are common Old World vultures.

 

© Webster 1913.