Coming up the driveway in the car a little before noon today (8 October 2011), I was surprised to see a very large bird flap out of the
trees, followed by a Blue Jay. I had just seen crows along the road, so it was evident that this bird was much larger than a crow and larger than any buteo. It was, in fact, a Turkey Vulture, the first I had seen actually within the woods in the 15-plus years since I arrived.
What, I wondered, was it doing here? Then the answer struck me.
The folk wisdom in southern Illinois, where I grew up, was that vultures, or buzzards, find carrion by the smell of rotting meat. But birds in general have a poor sense of smell, and the olfactory lobe of the brain, which is associated with smell, is large in mammals like us, but small in most birds. Then too, John James Audubon, an excellent naturalist as well as painter of birds, did a few trials in the early part of the 19th century, trying to assess how vultures found food. His observations of vultures failing to find hidden carrion led him to the conclusion that dead carcasses were located by sight. “The power of smelling in these birds had been greatly exaggerated,” he wrote.
Other observations didn’t always agree with Audubon’s conclusion. By 1964, an article by Kenneth E. Stager of the Los Angeles County Natural History Museum summarized his and other studies that pretty well established the main features of how vultures find their meals. In broad outline, Aububon wasn’t wrong, but he had worked mainly with Black Vultures (Coragyps atratus), which do locate food visually, either by spotting it themselves or watching Turkey Vultures (Cathartes aura). Turkey Vultures, it turns out, have a well-developed sense of smell which they can use to find even small animals that are not visible from the sky. They also have large olfactory lobes. Of course, they are not above gliding down to a dead animal they see lying out in plain sight.
There are some other details that may or may not have been decided in the last few years, such as whether either or both vultures can use the sight (or the sound) of carrion-feeding insects going to a dead animal as a clue to the corpse’s presence.
Earlier this morning before 9 AM, when I was walking down the driveway to get the newspapers, I had caught a strong smell of carrion. I left the driveway and only a few steps into the woods found a dead raccoon. I didn’t examine it carefully and have no idea how it met its death. When I had walked past the same spot several times yesterday, I had not smelled a dead raccoon. It was not there, or it was too fresh.
Finding a Turkey Vulture near a dead raccoon that it could not have seen from the sky doesn’t qualify as an important piece of evidence on the topic, Nevertheless, I was pleased that an observation of my own, right here in Oshtemo Township, is so nicely congruent with modern thinking on how the Turkey Vulture finds its food.
When I pulled up at the front door, I looked back and the Turkey Vulture had already returned to the trees above the dead raccoon. I ducked into the house, not wanting to interrupt the bird’s meal any longer.
A few hours later, I checked the carcass. The skull, vertebral column, and limbs had been stripped clean, and the skin was clean and much of it was inside out.