The turkey vulture problem

You see them soaring around Sisters all summer long; big, black birds wheeling in the sky, tipping this way and that as they catch the summer breezes: Turkey Vultures. (Not to be confused with the so-called, "wild turkeys" that perch on your back porch and poop on your lawn.)

Turkey vultures (TVs) are known to the scientific world as Cathartes aura. The Genus name Cathartes translates into "cleaning" or "purging," as in cleaning up the dead, and aura, "to rise, fly or glide high and with little apparent effort." So there you have it, an undertaker that flys.

For those of us who have gotten used to the idea of turkey vultures no longer being classified as raptors, but as short-legged storks, life has become more complicated. (Especially for publishers of field guides!) The AOU (American Ornithologist Union) - the last word in everything about birds in the U.S. - has released its 48th supplement to its checklist, and among the changes they have made are moving vultures back to the Falconiformes (hawks, falcons and eagles).

Re-evaluating the old evidence that placed them in with storks (where I think they belong), along with some new data makes the previous assessment uncertain. Though TVs have many characteristics that appear to be derived from ancestral storks, the AOU thinks the taxonomy of New World vultures still needs to be sorted out.

To make the debate even more complicated, the AOU refers to turkey vultures as "New World Vultures;" however, the majority of fossil forms of so-called New World species actually come from Europe.

"So what?" You may ask. Well, for one thing, it's important to know where animals belong in the world of persnickety biologists.

I'll bet you didn't know TVs, like storks, are said to cool themselves by urohydrosis (peeing down their legs). In addition, vague DNA work in the past suggested a link with storks. However, nit-picking taxonomists are hung up on the structure of the TV ear bones as they differ from storks. Storks have a tubular ear bone, a trait not shared with vultures - but, hey, TVs have bald heads, like some storks....

Then, there are the wings of TVs that are like those of hawks and eagles. However, the soaring ability of vultures is far better than hawks and eagles but at par with the beautiful white pelicans of the American West. Does that mean we should consider putting turkey vultures into the same family as pelicans?

Putting the TVs back in with the falcons, hawks and eagles doesn't make much sense if you look at the shape of their toes. Turkey vultures do not have strong feet and needle-sharp grasping talons. They have long toes with a slight web at the base, a foot well suited for holding down a dead deer while they tear at it with their bill (a sight and smell that's enough to gag a maggot).

The nostrils of raptors and TVs are slit-like. In turkey vultures, however, they're enlarged to aid the bird's incredible sense of smell. As far as I know, eagles, hawks and falcons cannot smell anything.

One feature that TVs share with Falconiformes is a nasal gland that will often secrete electrolytes, visible as drops of liquid from the nostrils while the bird is eating and thought to enhance the ability to conserve water. In one experiment a captive TV was kept alive and healthy for over a year without ever being given water.

No matter where you think a TV should be classified, they possess one trait that is extraordinary. Turkey vultures can ingest the most infectious disease you can think of, but when it comes out the other end, it's all sterile. That trait alone makes turkey vultures the most important member of Nature's cleanup crew.