Thursday, November 19, 2009 11:29 PM CST
Turkey vultures: nature's perfect cleanup crew
Esther Lutz, University of Illlinois Extension
One day last week, I came upon a dead fox squirrel as I walked along the roadway in my rural neighborhood. Having observed only gray squirrels on our property and in the yard, I was quite interested to see this different squirrel species. It was an adult male in fine physical shape and, although struck by a passing vehicle, was in remarkably good condition, perfectly intact. No blood, no entrails strewn about and smashed as is often the case with roadkill. I leaned over it and was thankful for the chance to examine the creature up close, however saddened I was by this life cut short unnaturally. It was a large and beautiful specimen with a thick and lustrous fall coat, totally in its prime. Feeling for a heartbeat and finding none, I noticed that the body was still warm to the touch. It had obviously been killed only moments before.
I remember thinking at the time what a fine easy meal the squirrel would make for a passing coyote, fox, raccoon or any of a myriad of other wildlife species that are opportunistic feeders. For them, it would be like hitting the jackpot for dinner — easy pickings and fresh for the taking. I picked the squirrel up by the tail, and gently tossed it into the grass off the pavement, sure that something would come along eventually and promptly dispose of it.
The next day on my walk, I noticed that the squirrel was still in the grass where I had placed it, and it didn’t appear as though it had yet been discovered. Nothing looked different; it remained untouched and intact as far as I could tell. The following day as I approached, I could see from quite a distance that there was something hunched over the carcass and patiently picking away at it. But it wasn’t any of the wildlife that had quickly come to mind when I first discovered the animal. The creature that had found the squirrel and was systematically ingesting its remains was a large, black, bare-headed bird — namely, a turkey vulture.
Cathartes aura — Turkey vulture:
The typical adult turkey vulture is 26-32 inches long with a wingspan nearly 6 feet wide. The body feathers are brownish-black, but the flight feathers on the wings appear silvery-gray underneath, contrasting with dark wing linings. The head is small in proportion to its body, red in color and bald in appearance, having few or no feathers. Its beak is short and hooked, ivory in color. The nostrils are unusual in that they are not divided by a septum; from the side one can see clear through the beak. A member of the group known as New World vultures (those inhabiting the North, Central and South Americas), this species has weak, chicken-like feet that are suitable for running on the ground. The turkey vulture is unable to lift, grasp or carry food with its feet; it can only step on it to hold it in place while eating. Since its bill and beak are not powerful enough to kill medium to large-sized prey, it eats primarily carrion (dead animals). Contrary to popular belief, however, it does not feed strictly on this. It will also feed on small mammals, reptiles and amphibians as well as on plant matter, including shoreline vegetation, pumpkins and bits of other crops.
Turkey vultures were given their name because the red, featherless head gives them the appearance of a turkey. Although the bare-skinned head is ugly, it serves an important purpose. While eating carrion, the bird must often stick its head inside the carcass to reach the meat. A feathered head would tend to capture unwanted pieces of the vulture’s decaying meal, along with all the bacteria that it hosts. Those rotting carcasses can get messy, but the bald head remains relatively clean. After a meal, the birds can often be seen perching in the heat of the sun, where anything that has managed to cling to the few bits of fuzz on the head will be baked off once and for all.
Turkey vultures have mastered the art of regurgitation. This behavior is vital in caring for the young (usually two chicks) as food must sometimes be transported over long distances to them. The bird will not construct a traditional “nest” but will scratch out an indentation in the soil or in a protected location such as a cliff, cave, rock crevice, hollow tree or in a thicket. One to three eggs are laid on a bare surface; there is little or no construction of a nest as such. Both parents incubate for 30 to 40 days, and the young are helpless at birth. They are fed regurgitated food by both parents and will fledge the nest in nine to 10 weeks, with family groups remaining together until fall. If the young in the nest are threatened, they may hiss and regurgitate to defend themselves.
The ability to vomit freely also enables the birds to “throw up” in the face of an attacker, the putrid smell of the rotting flesh mixed with the acids of the stomach becoming a very repulsive experience for a predator. “Lightening up” for an emergency takeoff could also be lifesaving for those birds too engorged and heavy to fly. Many times the food has not yet been digested, in which case most predators are happy to give up pursuit of the vulture in favor of this free edible offering.
Like most vultures, the turkey vulture has very few vocal capabilities. Because it lacks a syrinx, the vocalization organ of birds, it can only manage hisses and grunts. The olfactory lobe of its brain, however, used for processing smells, is very large when compared to that of other animals. This animal forages by smell, an ability extremely uncommon among birds, and completely absent in many. The bird flies low to the ground to pick up the scent of ethyl mercaptan, a gas produced when dead animals begin to decay. This heightened ability to detect odors enables them to search for and find carrion before others can.
Often on my walks I have observed our local population of turkey vultures engaged in seemingly unusual behaviors that I have found particularly puzzling. For instance, why do I often see large groups of them lined up next to each other on the tin roof of the local horse barn each morning at around 9 to 10 a.m., each in a standing posture with wings outstretched in the sun? (It brings to mind scenes from that old classic movie, Alfred Hitchcock’s “The Birds”!) How do turkey vultures fly so high and effortlessly without seemingly flapping a wing? And why, at a neighborhood bonfire on a Sunday afternoon in October, did we all observe an unusually high number of turkey vultures circling masterfully overhead? (I lost count at 60, and a neighbor said she was sure that she counted 75 or more. None of us had ever observed that many together at one time before.)
For answers to these and other questions, I sought out the advice of Jacques Nuzzo, program director at the Illinois Raptor Center in Decatur. Next month, stay tuned for his insights and expert knowledge of these unusual behaviors and of this misunderstood avian member of our Illinois landscape. We may even gain a new appreciation for the vital ecological role that this common bird plays the next time we look upward in our travels and see that familiar sight — a turkey vulture soaring gracefully far aloft, its distant black form silhouetted against the blue.
Esther Lutz is east-central Illinois master naturalist for the University of Illlinois Extension in Coles County.
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medic57 wrote on Nov 22, 2009 11:18 AM: