(Burrowing Owl Update Below)
Louis Kruk’s photos stand out for their flawless, striking composition and their tack-sharp clarity. Here he’s applied those virtues to a subject that many of us might prefer to see with a Doris Day filter in place — you know, blur out those blemishes, smooth out the skin, etc. But on this website we take our Nature straight, and Turkey Vultures are a very important part of it. Their scientific name, “cathartes,” means purifier. Without them, on our nature hikes we would have to thread our way through piles of smelly carcasses.
Their sense of smell was the center of a huge controversy among ornithologists for more than a century. Since Aristotle in Greek antiquity, vultures were credited with a strong sense of smell. But bird painter John James Audubon, staking a claim to authority as a scientist, maintained emphatically in 1826 that they had no sense of smell, nor did any other bird. In his recent book An Immense World: How Animal Senses Reveal the Hidden Worlds Around Us, (reviewed here recently), author Ed Yong writes that Audubon was responsible “for seeding a centuries-long falsehood about birds through some truly abysmal experiments involving vultures.” He put out a putrefying pig carcass, and no vultures showed interest. He put out a deerskin stuffed with straw, and a vulture came to eat. When these experiments came under criticism, Audubon’s friend John Bachman, a notorious racist preacher, defended him with even more bizarre experiments and emphatic claims denying a sense of smell to all birds. Yong writes that this “became textbook wisdom. Evidence to the contrary was ignored for decades, and the study of avian olfaction lapsed into neglect.” (Yong, An Immense World, p. 38.)
A 1964 article by ornithologist Kenneth Stager (Source) began to correct the mistake. In a review of Audubon’s experiments, Stager concluded that Audubon had confused the Black Vulture, which indeed has a poor sense of smell, with the Turkey Vulture. Papers pro and con relating to various vulture species continued to be published from the 1830s through the 1960s. Few if any of these studies went beyond the anecdotal. Stager was the first to study the matter using birds in the wild under controlled conditions, and with cross-reference to other vulture species besides the Turkey Vulture. He demonstrated conclusively that the Turkey Vulture has an excellent sense of smell. Other vulture species, less so. He validated the findings of biologists B.G. Bang and S. Cobb to the effect that the Turkey Vulture has an exceptionally large olfactory anatomy, including nostrils, olfactory bulb, and related brain regions. These are much more developed than in other vulture species, and are among the largest of any bird species studied. Stager also corroborated the observations of oil companies, which used gatherings of Turkey Vultures to detect leaks in their natural gas pipelines. The gas contained ethyl mercaptan, which smells like freshly decomposing meat. Since Stager’s paper, numerous other studies have corroborated the Turkey Vulture’s well-developed sense of smell, and opened the doors to studies of olfactory powers in other species, including kiwis and albatrosses, petrels, shearwaters, and fulmars. Today, Audubon’s and Bachman’s claim that birds cannot smell is thoroughly discredited.
Vultures in general, a genus to which the California Condor belongs, have excellent vision. Most species when foraging fly relatively high, affording them a large field of view. Turkey Vultures commonly forage at low altitudes, where they have a better chance of sniffing freshly dead meat on the ground, visible or not. Other vulture species use the Turkey Vultures as scouts, and when they see them descend to the ground, they plunge in and try to take over the meal.
Turkey Vultures aren’t strangers to Chavez Park. I’ve had some luck filming one in flight and a pair taking the sun on the ground. More recently, I filmed one walking some few steps on the mudflats near the Schoolhouse Creek outfall, as if it were a shorebird. It’s not nearly so graceful on the ground as in the air! But it showed a remarkable takeoff power. It didn’t have to run or hop to get airborne. One or two powerful flaps of those wings against the prevailing westerly breeze and it was up. Here’s that video:
Burrowing Owl Update
There is no point my posting a video of the Burrowing Owl in the park this morning. I could stay only a few minutes, and during that time the bird hardly moved. It swiveled its head left, forward, and right in a leisurely way. The light rain falling at the time didn’t warrant its attention. Once again, like yesterday, it looked like it probably spent the worst of the night’s downpour in shelter, and came up and out for the daylight just slightly moistened.
Yesterday afternoon during my nap we had a hailstorm in Berkeley. I regret not being in the park at that time to see what the owl did with it. Maybe I’ll get another chance.
The owl has remained in Perch B now for ten days in a row, a record for the season. The calendar of its perches so far is at this link.