Written by Mike Armstrong
Everybody knows something about the California Condor: endangered, awesome and so on. But this article is about one of his relatives that isn’t endangered but is useful, graceful, and interesting – the Turkey Vulture (Cathartes aura), a frequent visitor to Bolsa Chica Ecological Reserve. He is probably the largest bird that most visitors to Bolsa Chica will see—nearly eagle-sized with a 6’ wingspan, black, and usually in flight, either circling ‘way up high or soaring low along the Mesa face.
What’s in his name? A “turkey” he isn’t, but the red, bare-skinned head of the adults does resemble a hen turkey’s, his black plumage is “turkeyish,” and his size (but not weight) is fairly close to some wild turkey species. But he doesn’t fly anything like a turkey, doesn’t eat the same stuff, and nests in very un-turkey-like places, and doesn’t gobble nor cluck! Turkey vultures are silent except when you threaten them or their nests. Then they can hiss like a spitting cobra and are likely to projectile vomit their chicks’ next meal onto you. You won’t be back.
Even the “vulture” part of their name isn’t simple. Vultures in the Americas are only distantly related to the Old World vultures, but both are related to condors, eagles, and hawks (updated information/ source tolweb.org). Ours are related to condors, eagles, and hawks; theirs to storks and cranes. Their uncanny similarities in physical appearance, migration and nesting habits, and feeding are striking examples of “parallel evolution.”
Vultures are associated with death in many cultures, including ours. But this black, silent creature makes an interesting, useful life out of others’ deaths.
Turkey Vultures have been here a very long time! They are among the most common bird fossils found in the La Brea Tarpits, along with their California Condor relatives and several even larger extinct vulture-like relatives. The tar trapped huge mammals, seeming a huge feast for these scavengers, but some of them fell into the same trap as their intended meals. Many of the creatures preserved at La Brea have gone extinct, but not ‘ol Cathartes aura! He’s survivor because he’s a good adaptor.
Turkey Vultures nest high on cliff walls, not in trees, because they lay their one or two eggs a year directly on inaccessible rock shelves that form warming “heat sinks.” Vultures normally only lay one or two eggs a year, sometimes none in lean times, keeping their populations down to levels a scarce food supply can sustain. Many that we see here come from the Santa Ana Mountains’ canyons.
Vultures “hunt” for food in the same sense that we “hunt” for gold, not the sense that hawks or eagles hunt for prey. They occasionally kill small animals when they are extremely stressed by winter hunger. But normally they must find an animal that has been killed by a natural predator or by man. That means that their skills are all about finding, NOT killing. They can fly over thousands of LIVE potential food animals and not find any food at all! This means that they must be able to traverse IMMENSE amounts of habitat. Where do they get the energy, if the food supply is so slim?
First of all, they are incredibly efficient flyers—they travel long distances with a bare minimum of muscular and respiratory effort. Their brains are attuned to “trimming” the position of their wings and even individual flight feathers to give the greatest lift with the least muscular movement.
Vulture wings are long and tapered. If you have ever seen a sports glider, you’ll see the similarity. Gliders, like vultures, mainly soar using both solar thermal power (the power of rising heated air currents) and, oddly, the opposite pull of gravity. But vultures don’t have a tow plane to get them up to soaring altitude, so they have to find alternate sources of power to avoid expending too much energy in the “takeoff.” This is one reason vultures prefer to perch between flights on a very tall tree or the edge of a cliff, to “launch” downward using the pull of gravity to speed them downward into the wind until they can zoom upward using their diving speed and the added lift from the wind’s speed. Having gained altitude, they zoom up and down, and with a little bit of correction by wing flaps, find either a thermal air current or, if they are searching at low altitude, a “wind wave” along a raised feature like a cliff or steep mountainside.
Hikers along the Mesa Trail just above the waters of Bolsa Chica are often startled to have a BIG black bird zoom along parallel to the trail just off the mesa’s edge. Vultures use the rising air “wave” that the offshore breeze causes when it hits the edge of the mesa to “surf” along the cliff front, looking for dead rodents, or dead marine animals or birds left by the tide. No flapping when they do this, just zooming and looking and smelling.
“Wind waves” occur when there is a wind blowing against a cliff, a peak, or a mountain range which “bumps it up.” “Thermals” occur when the land heats the air above it so that it rises strongly. Both gliders and vultures “ride” that rising air, expending only tiny nudges of energy needed to steer. Since thermal air currents caused by large masses of land or rock absorbing the sun’s heat can rise thousands of feet, a bird can turn that energy into many miles and hours of flight.
Vultures are usually late risers because they use the early sun’s energy wisely. At night, they can drop their temperature to a near hibernation level to save energy. When the sun rises, they wake and open their big black wings wide up like solar panels to warm back up to their normal body operating temperature. When the sun has been up long enough to heat up, they dive off the heights to find a thermal!
Once at operating altitude, they use several skills to search the area for food. Like many of their relatives, they are “eagle-eyed”! But unlike most birds, they are also “wolf-nosed”! Turkey Vultures prefer fresh carrion. They have extraordinary smelling abilities to find a relatively fresh carcass from great heights, even when it is obscured from above by vegetation. But when they smell something, how do they find it and verify that whatever killed it isn’t waiting to kill any freeloaders? That all involves the flight pattern of vultures that we see most—circling in what are called “gyres.” These circles widen and rise when the bird is searching, tighten and lower when food is sensed.
Once a prospective meal is detected by odor or sight, the bird circles in ever-smaller, ever lower orbits until it gets either a verification of the meal by odor or vision. But even if all seems safe, it doesn’t drop right down on the dinner table. Survivors are careful. Once a vulture lands, it is vulnerable. Taking off is risky—wastes a lot of energy and a takes a longish liftoff low to the ground – an easy target for scavenger competitors like big cats or wolves.
Carnivores that kill large prey have a standard routine. Kill, eat your fill, sleep, eat more, but sleep nearby so you can chase away thieves. So, vultures are wary and take their time casing the restaurant —circling, circling, looking, smelling.
We often see Turkey Vultures circling far away, and so do other Turkey Vultures. That signals them that a potential meal may be below their distant fellow, and they come to see. This often results in a spiral formation of two or more vultures, sometimes many more, circling above the prospective food. Such a formation, whether for feeding or for social purposes during migrations, is called a “kettle.” Vultures and their hawk kin do it during migrations, gathering in display above certain “traditional” thermal-generating mountains (often named “Hawk Mountain”). But only vultures do it for food sharing.
This seemingly solitary bird’s cooperation surprised me. But it makes sense.
Nature, contrary to “Social Darwinists,’ often isn’t the raw “Law of the Jungle” arrangement Jack London dramatized. Many creatures (and even plants like forest trees) cooperate among their own species and even between species. More shared food for more vultures means more of the species are likely to survive.
And the environment that vultures evolved in probably had something to do with their sharing habits. The Age of Mammals was really The Age of HUGE Mammals. Big predators killing and eating big herbivores. Say a giant extinct jaguar ambushes and kills a half-ton ground sloth. He can’t save all the meat from competitors by eating it at one sitting.
So, he “sleeps it off,” and, while he is sleeping, vultures silently drop from their orbiting “kettle” and help themselves. Once one of them is full, he stands guard, looking for the returning cat or other dangers. If one appears, he flaps away noisily, warning the rest of the kettle to get airborne! They fly away to feed their chicks and/or nesting mate, if any, or just digest someplace up high for an easy launch in the morning.
The Turkey Vulture’s black color warms him up fast when the sun is up, and it also serves to show him to his fellow vultures at a very long distance, should he be lucky enough to score another carcass or find that the jaguar left enough to share. If not, he too can see his fellow vultures far away, and, if a couple of them should start to gyre downward, he has the option of jumping into their kettle!
Life is probably harder for Cathartes aura in California now that the Age of Mammals has become the Age of Man. Meat, live and dead, is scarcer in the wildlands; habitat for roosting and nesting is shrinking. The Spanish and Mexican cattle ranchos were a brief return of a lot of “easy meat” because there were millions of big herbivores again. They died all sorts of ways, and the meat was mostly eaten by scavengers–not humans–because the “cash crop” from cattle ranchos was “cuero, cuernos y manteca” (leather, horns, and lard), not meat. After a typical “matanza,” (slaughter roundup) a huge pile of cow carcasses was usually left for the grizzlies, wolves, coyotes, condors–and vultures. But when drought destroyed THAT era of excess, the California Condor and its relative the Turkey Vulture declined toward their present state–near extinction for the first; precarious stability for the second.
What do Turkey Vultures eat today? Any dead mammal big enough to smell or see from a height attracts them. Unfortunately, that often means “roadkill”—deer and smaller animals that get hit by autos and trucks at night. We have become the top predator, by far, and our primary means of predation is automotive, not ballistic.
For the vulture this is good and bad news. As long as there are cars and deer and other animals whose instincts don’t equip them to deal with a giant metallic killer that goes 70 mph on the ground (much faster than the several species of cheetahs California had back in the Age of Mammals) and projects blinding light in its path, vultures will have meat. Unfortunately, they are not equipped to get airborne in the time that a car or truck can blow over a dead deer, coyote, or jackrabbit. Our tar-topped roads sometimes become the new La Brea for Cathartes aurus, killing food for him, attracting him to it, and killing him beside it.
Chemicals and other toxins have reduced the number of Turkey Vultures in California. The ban on DDT has helped restore their fertility and stabilized their numbers; the ban on lead in ammunition for hunting is intended to help them as well.
I’ve heard the Turkey Vulture, like the Condor, called a “living fossil.” I prefer to think of him as a surviving veteran of the Big Extinctions, huge climate changes, and the invasion of California by humans at the end of the Ice Age and again in the 17th Century.
But what’s really important is that he still soars and we can keep him that way by keeping our wildlands WILD, so he has perches to rest, nest, and warm on, and to launch and soar from.
*If you happen to see a Turkey Vulture with a white wing tag, you can report it for scientific research. Bloom Biological, Inc. has been studying Turkey Vultures here in Southern California for their 20+ year ongoing research project. Their research project includes monitoring lead toxicity as well as migratory and dispersal patterns. Read more about their research and how to report a sighting on their article: Wing Tags on Turkey Vultures
photos by: Tohid Azimi, Alan Wendell, E. Chin