Comox Valley Naturalists Society
On the Wild Side . . .
The Carrion Eaters
On hot summer days, the skies over Vancouver Island are home to the turkey vulture. Many resident and tourists alike are surprised to learn that these large black birds soaring over head are not the American bald eagle. This error is understandable, as both are large dark birds that are masters of catching thermals and soaring with a minimal amount of energy expended.
A shared characteristic of vultures and eagles is their diet of carrion. These birds are nature’s clean-up crew. Like their human counterparts, the task is as essential for the smooth functioning of an ecosystem as it is for the maintenance of a town. A trash collector’s strike quickly results in civic dysfunction. An ecosystem without carrion eaters would be in a similar state of disarray. The Turkey Vulture's scientific name, Cathartes aura, meaning "pacifier" or "cleanser."
separate the eagle from the vulture is simple close up. Although of roughly
similar size, the vulture with its bright red feather-less head
is quite distinct from the white headed bald eagle. However, as the vulture
is most at home in the air, most identification must be done from afar.
From the distance the vulture can be identified by the angle that it holds its wings. The wings are held at a shallow “V” which is known as a dihedral. The bald eagle in contrast holds their wings horizontally. Another clue is what I call the ‘vulture wobble’. As they circle and soar they often have a slight wobble unlike the eagle which seems much more controlled in its flight.
Although both the vulture and the eagle are large dark birds, looking at their wings when they soar above gives another clue to separate these two. The turkey vulture’s wings often appear to be two toned, unlike those of an eagle. The lighter grey of its primary and secondary feathers gives it this effect.
The turkey vulture illustrates the biological principle of form determining function, a case in point being its featherless head. As a carrion eater its head is often immersed in putrefying gore. Feathers on the head would be quickly soiled and rendered useless. The vulture has simply done away with them altogether. Although its principal food is carrion, studies have revealed that close to 50% of the vultures diet is in fact vegetation.
Unlike the raptors, such as hawks, the vulture has relatively weak talons. These cannot be used to grasp and tear at live prey. Food is carried back to its nest only in the bird’s crop, as its feet are not strong enough to carry food. The vulture has adapted to a role as scavenger and not a predator. In fact taxonomically the vultures are more closely related to the storks than they are to members of the hawk family. An anatomical clue to this is seen in the foot of the vulture. These resemble the feet of storks with a small amount of webbing between the toes.
Science has much to learn from the turkey vulture. Unlike many birds the turkey vulture has a keen sense of smell. It can detect smell in the parts per trillion range. This bird can consume infected, diseased carrion, with no ill effects. Its digestive system can neutralise harmful bacteria and viruses, and the excrement it produces is sanitized. Unlikely to appear on flag or a coat of arms, the turkey vulture is none the less a fascinating creature playing a vital role in ecosystem function.
Click on a link below to view the CVNS newspaper column.