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.
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