In an article last month I wrote about a bird commonly seen in Illinois, the turkey vulture. I have lived in east central Illinois all of my life, and they have certainly been a familiar sight over the years, perennially soaring above the landscape on effortless wings. When I encounter them during walks in my rural neighborhood, I sometimes am able to get pretty close to them before they flap their wings and rise up and away. They really are quite large. Oddly enough, this bird that I used to view as having a rather dirty lot in life (that of a lowly carrion-eater), soon became an object of my curiosity as I continued to occasionally catch sight of some of their strange behaviors. And the more I observed them, the more fascinating they became.
In our rural neighborhood, we have quite a large local population of turkey vultures, also called turkey buzzards. Our area is characterized by pastures, grassland, farm fields, and some wetland areas and is relatively open with a few slight hills. It also provides nearby woods but is not heavily forested, a favorite habitat for these birds, highly suitable for nesting and roosting.
This species is a gregarious one, and gathers to roost in large community groups in the early evening, generally breaking away from its fellows to forage independently during the daylight hours. It prefers to roost in dead, leafless trees, and that is often where I see them each evening, just before the sun sets. It's quite a sight, the smattering of numerous dark, black forms sitting motionless high in the tree branches, silhouetted against the evening light in the west. I once counted their numbers out of curiosity, and was surprised to find that there were more than 140 of them roosting together one evening in a group of four trees on a ridge along the roadway near my home. I see them every evening there, and it truly is an impressive and unusual sight to behold.
The constant presence of turkey vultures in my neighborhood has led me to observe some rather odd habits from time to time. I contacted Jacques Nuzzo, program director from the Illinois Raptor Center in Decatur, hoping that he could help answer some of my questions as to why these birds sometimes exhibit such strange postures and amazing flying maneuvers. Following are some of my observations of wild vultures and Mr. Nuzzo's explanation of these puzzling behaviors.
Why do I often see large numbers of turkey vultures lined up next to each other on the tin roof of a horse barn every day in the middle of the morning, each in a standing posture with wings outstretched in the sun?
It is not unusual to often see turkey vultures standing in a spread-winged stance. This standing posture is believed to serve multiple functions: warming the body after an inactive and cold night, drying the wings, and baking off bacteria gained from eating rotting flesh. It seems to be practiced more often after damp, cold, or rainy nights. In addition, these birds often find that their long wing feathers must drag along the ground as they feed on carcasses and peck at the flesh inside of the dead bodies. This can cause the feathers near the tips of the wings to become bent and misshapen, making smooth flight difficult to maintain. The act of stretching the wings in the heat of the sun helps to straighten out those wing feathers and return them to "flight readiness."
How do turkey vultures fly so high and effortlessly without seemingly flapping a wing?
The turkey vulture is fairly awkward on the ground, and has an ungainly, hopping walk. It really must put forth a great deal of effort in order to launch itself upward—it flaps its wings while pushing with its feet and hopping off the ground. But when it reaches the upper air, it becomes a true master of flight. The vulture holds its wings in a shallow V-shape and often tips from side to side as it soars. The flight of the turkey vulture is considered to be a classic example of static soaring flight—the wings are flapped very infrequently as the bird takes advantage of the rising thermals (warm, upper air currents) to stay soaring. The action is at once both effortless and motionless as the wings catch and float on the air currents high above the earth. It can stay aloft for long periods of time, simply soaring masterfully with little or no physical exertion.
Why was there a large group of turkey vultures (75 or more) circling high above our neighborhood bonfire on a late afternoon in October? Were they attracted to the smell of the food on the picnic tables or perhaps the hot dogs roasting?
Turkey vultures have a good sense of smell, but they are only attracted to rotting flesh. They really prefer flesh that is about one day old, and are most able to pick up the scent of the ethyl mercaptan (the gas given off when animals start to decay) at that time. What you observed that day was a "wake" of vultures, a local group of turkey vultures that was forming up in order to migrate out of the area. Most often, you will see this behavior in the early spring or late fall. Turkey vultures don't "have" to migrate, but they often do when it starts to freeze in the environment and the carcasses upon which they feed become frozen. The beaks of the birds are not powerful enough to break into the frozen carcasses in order to feed, so they must migrate south to warmer temperatures where food is available to them. They usually only travel as far south as needed to where it doesn't freeze, but some may make it on to Florida or even further south. Then around March they will start to migrate back to the northern areas. In a wake such as you observed, you are seeing your local population as well as many others from the surrounding areas coming together in one location to form a migrating group. That would account for the large number together at one time. There may have been one or two coming to check out the gathering, but not the huge numbers that you saw. It was just a coincidence that the "wake" happened on the day of the cookout, and you were all outside to observe it.
There is no doubt that the turkey vulture's habit of feeding almost exclusively upon carrion has caused us to regard it as something that elicits a feeling of repulsion and disgust. This species scavenges efficiently, and while they do not easily locate freshly killed animals, they readily find them when they are one day old, and do in fact prefer day-old carcasses to older ones. They have an unsurpassed ability to exploit almost any open or forested habitat in finding a wide range of food sizes and types. Vultures are among nature's most persistent scavengers, and as such perform a useful service wherever they are located in the world. They play an important role in the ecosystem by disposing of rotting carcasses that would otherwise litter the landscape and be breeding grounds for disease. In so doing, they help convert the nutrients of the dead back into the nutrients that support the living.
The turkey vulture is, however, one of nature's great inventions when considered from the viewpoint of its mastery of the sky. Perhaps the grace and beauty of its flight may in some measure serve to redeem it and help us for a moment to forget its lowly and disgusting feeding habits. The great nature writer, Bradford Torrey, once remarked of the turkey vulture that, "One might almost be willing to be a buzzard to fly like that." When we observe one or more of these great birds in our summer skies soaring far aloft with their six feet spread of wings effortlessly riding the thermal currents, we are forced into at least momentary admiration of the ability of a bird to make itself completely at home in the upper air. The vision of the turkey vulture soaring gracefully far aloft is enough to remind us to admire and appreciate a creature that, long before the advent of the airplane, had succeeded in complete and perfect mastery of the air.