Turkey vultures may not be pretty, but they serve important purpose
I've seen as many as four turkey vultures perched in a dead tree here at the nature center, but most of my recent vulture insights come from watching our resident bird.
She will give you the once-over with her eyes. As you return the gesture, you would do well to recall that the vulture adorned the statue of Isis in ancient Egypt. Vulture and humans have been eyeing each other through the ages.
The human's opinion of a vulture has not always been an affable one. Take, for instance, these opening lines taken from a 19-century vulture poem by the Rev. T.C. Porter:
"Prophet of evil! bird of omen, foul!
Unstained by living blood,
Corruption is thy food;
How man abhors thee, horrid ghoul!"
His poem does not exactly paint a pretty picture. In some areas, though, returning turkey buzzards are seen as harbingers of spring, Let's take a closer look at these increasingly common summer residents.
Is a vulture a buzzard?
It depends on where you are. If you are celebrating Buzzard Sunday in Hinckley, Ohio, you are welcoming the mid-March return of turkey vultures to the area. If you are photographing a jackal buzzard in South Africa, you are not focusing on a vulture. Instead, you are zooming in on a buteo, a genus of hawks.
Buteo comes from the Latin butes, which refers to broad-winged hawks. This Latin term also gave rise to the old French word busart, which led to buzzard. So, for the most part, in the New World buzzard refers to a vulture while in the Old World it refers to a buteo.
Of course, both buteos and vultures have broad wings. Vulture wings, however, are much larger. The largest buteo commonly seen in our area, the red-tailed hawk, has a wingspan of approximately four feet. The turkey vulture measures close to six feet from wingtip to wingtip.
In fact, the only raptorial bird large enough to confuse with a turkey vulture is a bald eagle. So, how do you tell them apart? The flight profile, looking head on, of a bald eagle is flat. Turkey vultures hold their wings in a shallow "V," called a dihedral, and are similar to the wings of some hang gliders.
I can't help but think this wing arrangement is highly energy efficient, so to speak, as turkey vultures rarely flap their wings. Instead, they tilt and tip from side to side as if balancing on an unseen high wire.
Up close and personal
At close range, a turkey vulture won't be confused with any other bird of prey because, unlike a bald eagle, the vulture is really bald.
While a small, red-skinned head is not particularly attractive, it is an example of form following function. Think about it. You make your living slurping down the guts of road-ripened raccoon, deer, rabbit, and opossum. When your head comes out of those rotting body cavities, it is covered with bacteria-laden slime.
Now, what kills bacteria? Ultraviolet light from the sun. How to maximize the amount of sun hitting sticky skin? You got it, less feathers.
Not surprisingly, vultures are amazingly resistant to most diseases found in carrion, such as botulism and salmonella.
As if these adaptations aren't interesting enough, let's move from the head end to the other end of a vulture. In birds, you see, feces and urine are combined and voided through a single opening or vent.
Why am I telling you this? Keep in mind that birds don't sweat. What good would sweat-soaked feathers be if you needed to fly away?
Now, picture our bareheaded and barelegged vulture perched on a rocky ledge on an extremely hot day in, say, an Arizona desert. There's no water nearby and you need to cool down. What's the solution?
Well, the scientific term is urohidrosis. In other words, the bird directs the cloaca downward and forward to defecate on the legs or feet. Just as with sweat, the liquid feces evaporates and the vulture is cooled down.
In addition, uric acid in the poop helps kill germs on the vulture's feet. (Think about where those feet have been.) Neat, eh? Hmmm, maybe not so neat.
Interestingly, other groups of birds, such as boobies and storks, excrete on themselves to cool down. Traditionally, vultures were grouped with diurnal birds of prey based on their hooked beaks, plus similar migratory and feeding habits. However, due to behavioral (i.e. urohidrosis) and genetic studies, their relationship to storks has been accepted.
The question that scientists have wrestled with is when did our New World vultures split from the stork branch in the ornithological family tree? Suffice it say, it was a long, long, time ago.
It should not come as a surprise that turkey vultures have a great sense of smell. Even with their excellent eyesight, soaring vultures aren't going to be able to spot a dead raccoon lying under a stand of trees, but they will smell it.
In fact, vultures have been attracted to the aptly-named stinkhorns, mushrooms that smell like decomposing flesh. The stink attracts flies, which land and then spread the mushrooms' sticky spores.
To be precise, the vulture-attracting gas emitted by carrion is ethyl mercaptan. When looking for leaks, natural gas companies have learned to introduce this odorant into pipelines, then all they have to do is look for where the vultures are circling.
Persecuted in the past
The attitude expressed in Rev. Porter's poem led to unnecessary vulture deaths long after it was generally acknowledged that vultures are beneficial scavengers. During the early to mid-1900s, for instance, Texas ranchers killed more than 100,000 black and turkey vultures.
Given their ability to smell rotting meat, vultures also ran afoul of poisoned baits and leg-hold traps set out for various other predators.
Nowadays, the valuable role played by vultures is generally understood. I like to think that most of us who have seen a vulture picking at a dead possum or raccoon are glad to know that the unfortunate animal's death is being cleaned up and utilized.
Even Rev. Porter recognized the vulture's important role. Despite his initial harsh words, his vulture poem continues:
"And yet thou art a minister of God
To rid the world of pestilence and taint;
Thou sparest both the sinner and the saint
Under the sod."
• Mark Spreyer is the executive director of Stillman Nature Center in Barrington. He can be reached at firstname.lastname@example.org.