Josephine, breathless and wild-eyed, found me in the kitchen. “Papa! There’s an eagle!”
“Do you mean a seagull?”
“No, an e-gull!” She pointed outside.
I wiped my hands and followed her to the door. We got there just in time to see a black bird taking off from a tree, powering into the air on wings that might have been longer than my arms. Maybe it was an eagle—a golden eagle, perhaps? Then I saw the scrawny red head. It was a turkey vulture.
I’m generally disappointed when I see turkey vultures. Whenever I see something vaguely raptorlike gliding across the sky, I’ll stop to see if I can identify a hawk or falcon—respectable birds worthy of note. But then I’ll see the fingerlike feathers spread wide at the wingtips or the white on the underside of the wings and think, Oh, just a turkey vulture.
But after a year of researching wildlife so ubiquitous they are invisible, I couldn’t turn away, or tell Josephine that her enthusiasm was misplaced. So what do we know about turkey vultures?
The answer: Not much. Turkey vultures have deflected the attention of scientists just as effectively as they had deflected mine. They are the introverts of the avian world, silently doing important work while more entertaining birds get all the love. This only made them more interesting to me: The more invisible a creature is, the greater its potential to enrich my life. Douglas Long, a biologist and longtime turkey vulture enthusiast, is going to write the first book on these birds as soon as he can get to it. When I asked around, several people told me that Long was the person to talk to about turkey vultures, and I began pestering him with e-mails. Eventually, we got in touch. He told me there are huge gaps in our understanding of turkey vultures. And that’s odd, because they are so big, so readily visible in the sky.
“I think turkey vultures are probably the biggest least-studied birds in North America,” Long told me. “What we know about golden eagles or bald eagles could fill books. No one has written a book on turkey vultures. Not that much is known about them.”
“We have no real idea of what the current population is and what it was historically,” he told me. We don’t know how long they live, though there’s a forty-year-old bird in captivity. “It’s not like you cut off the wing and count the rings.” Though we see the birds all around North and South America, scientists don’t have a handle on their distribution or movements. These very basic facts about this very common bird are simply unknown. Turkey vultures are like an unassuming neighbor that you frequently see, but if you start asking around, you realize no one has ever talked to the guy. And all of a sudden, what had seemed too banal to notice becomes mysterious.
I mistake turkey vultures for hawks or falcons because all these birds are gliding strategists. All raptors are excellent gliders, but turkey vultures have mastered the art. They set their wings open and make only the subtlest muscular adjustments to maneuver. In this way they are able to hang on the breeze, expending minimal energy. They circle, buoyant in thin air, searching for food. An adult turkey vulture may take to the air in the morning and, after some gawky flapping to hoist itself skyward, spend the next twelve hours aloft, motionless as it traverses vast expanses. Turkey vultures spend 90 percent of the daylight hours soaring, Long said. They ride rising bubbles of warm air called thermals up to 5,000 feet, then spiral slowly down. They can go higher—up to 20,000 feet. We only know they reach that altitude because they have hit airplanes far above where pilots expect to see birds.
Long had agreed to meet me at a brewery. He told me to look for “the chubby middle-aged guy in a Hawaiian shirt.” I wouldn’t call him chubby: He has a Falstaffian solidity, and the jovial bonhomie to match. Long’s interest in wildlife biology stems from a childhood filled with animals, he told me. As a baby, he slept alongside cats in his crib, and there were many more creatures in the backyard of his Orange County, California, home. “In the place where neighbors would have swimming pool or a tennis court, we had a walk-through aviary filled with birds and a koi pond.”
This interest in animals eventually took him to the California Academy of Sciences, where he did research on sharks, birds, and manatees. He also established a turkey vulture colony on the roof of the museum and began delving in to the mysteries of these strange birds.
Long and I found a table on the roof deck of the brewery. I bought him craft beer and peppered him with questions. To start off, I wanted to know why turkey vultures stay up in the air for all those hours on end.
“Well, right, that’s one question,” he said. “Presumably they spend all that time in the air because it’s hard to find food; they have to move around a lot to locate dead animals. But that raises all sorts of other questions.” How do they eat carcasses without getting sick? How does their extreme mobility affect their lives? Do they return to regular homes? And how do they manage this life suspended in midair when they have to molt and replace their feathers? One of the most stubbornly bewildering mysteries about turkey vultures, he said, has to do with their strange proclivity for pooping on their legs. Several common theories attempt to explain this, but none stands up to scrutiny. “You’ll see these ‘fun facts’ about turkey vultures on the Web,” Long said, “and they’ll often say turkey vultures defecate on their legs to cool off. Well, in this colony we had in San Francisco, they were doing that in the coldest part of winter.” So that doesn’t make any sense. This awkward mystery concerning a sometimes-awkward bird, I figured, was a good place to start.
Here’s a slightly better explanation for the leg pooping: It armors the vultures by covering their feet with good germs that fight off the pathogens swarming in their food. This is plausible: Turkey vultures are always coming into contact with virulent microbes, and they have other, similarly bizarre means of protecting themselves.
It’s not that turkey vultures like rotten meat, Long said. When he gave the birds in his colony a choice, their preferences were always clear. “We did simple experiments,” he said. “Here’s meat from a dead sea lion that’s been on the beach for a week, and here’s fresh meat that we just got in Chinatown. They went for the fresh stuff, always.”
But they generally eat rotten meat, because that’s what they can find. Turkey vultures use their noses to detect the chemicals produced by decomposition, then zero in on the source. This capability is unusual—most birds have a weak sense of smell, or none at all. You sometimes hear that you aren’t supposed to touch a baby bird because the mother will reject it if it smells wrong: “It’s a myth,” Long said. “The mother would never notice the difference.” Turkey vultures, on the other hand, are equipped with olfactory organs that can pick out a few molecules of decay, even diluted in the wash of high-altitude wind. When a turkey vulture detects the scent of rot, it circles down, tracing the plume of chemicals to its source. They are so good at zeroing in on dead things that other animals use them as guides. California condors, for instance, don’t have such a great sense of smell, so they follow turkey vultures and then bully the smaller birds away from the prize. Humans also watch turkey vultures: In Florida, a Dade County Sheriff’s officer told Long that he will always check when he sees the birds circling, because you never know—it could just be a dead alligator, or it could be a human body.
Once a turkey vulture finally lands beside its festering quarry, it faces a more formidable challenge: It has to actually eat the thing. Sometimes it’s a healthy animal that a car dispatched, but other times it’s an animal that died from disease. The vultures have no way of differentiating between diseased and healthy as they gulp down the raw meat and organs. But turkey vultures have incredibly powerful stomach acids that seem to wipe out anything they touch. “This has been the subject of a lot of curiosity, but very little medical research,” Long told me. “They will eat something with a very high E. coli or Listeria load and they will be fine. They can eat stuff that’s tested positive for rabies, Hantavirus, cholera; when it comes out the other end, there’s just no trace. They are virtually indestructible.”
In the 1930s, after an outbreak of hog cholera in livestock, the USDA worried that turkey vultures were spreading germs and advised farmers to shoot them. As we now know, the birds were actually doing the opposite: disinfecting tainted meat in the crucibles of their stomachs.
Still, Long doesn’t exactly buy the idea that turkey vultures poop on their legs as an extension of this microbial warfare. The problem, he said, is that the bird’s legs don’t have a lot of contact with the carcasses. Their faces, on the other hand, are covered with germs. The vultures have a hard time breaking through tough animal hides, so they frequently find one opening—yes, sometimes it’s the anus—where they insert their heads. One study found 528 different types of microorganisms on turkey vultures’ faces (compared to just 76 in their guts). “Maybe their poop kills germs, but most of the germ contact is on the face,” he said. “So if that’s the explanation, they should be pooping on their faces.”
They don’t do that. Another theory bites the dust.
A turkey vulture has barfed on Long, providing him with a firsthand experience of the stomach detoxification process.
“It smells absolutely abhorrent,” he said. “It’s hard to wash off your hands. It’s one of those smells you wash three or four times and it’s still there.”
“And it smells like rotten meat?” I guessed.
“It’s rotten meat, plus. Maybe it’s that super enzyme they have in their stomachs, or maybe it’s some sort of beneficial bacterial. It’s penetrating, and super distinctive—a special turkey vulture smell.”
It was one turkey vulture in particular that would puke on Long. One of the birds in his colony had imprinted on humans when it was young, and it acted more like a puppy than a vulture. It would affectionately lean on you, Long said, and begged to be scratched on the neck. Turkey vultures in the wild are almost asocial: They roost in groups, but they don’t interact with, talk with, or preen each other. But they are also very clever, and this particular bird had simply learned how to emote in a way that humans could understand.
In any case, Long would take this bird to demonstrations and school lectures. He’d simply put it in the back seat of the car, which always worked fine unless he had to drive a particularly windy road. Then it would get carsick and vomit, and the whole car would stink for weeks.
Turkey vultures seem to use their vomit as a form of defense. If threatened by a larger animal, they will extend their wings and hiss. If this doesn’t work, they vomit up their last meal. This may startle the aggressor, or it may simply lighten their load so they can take to the air more easily. It might also be an offering: Eat this, not me. Long has seen coyotes surprise turkey vultures with what appears to be intention and then gobble up the smelly regurgitated mess. Isn’t nature beautiful?
Why, then, do turkey vultures poop on their legs? The short answer is that no one knows. It’s another secret hiding in plain sight. Long does have a hunch; he calls it a “crazy idea” to make it perfectly clear that he hasn’t tested it in any scientific way. But he has spent enough time watching turkey vultures to have a sense of how they work and suspect it may have something to do with signalling identity.
The birds he kept on the roof of the California Academy of Sciences all looked very similar, but he said “it was easy to tell which was which from their personalities.” There was Friendly the affectionate bird, Tennessee Jack the delinquent teenager that loved running behind houses at night and stealing dog food until someone caught it with a pool net, Lumpy, Droopy, and Maggie, who was alert and ornery. The five of them were all intelligent, curious, and incredibly destructive when bored. (“They figured out how to dig up the wood chips, and then found the corner of the tarp under that, and then they peeled the tar paper off the roof,” Long remembered. “So I would have to do things like bury dead rats under layers of cardboard to keep them occupied.”) And he noticed that whenever the birds encountered each other, each would lower their heads to the level of the other’s legs. Were they sniffing?
Though Long could easily recognize the birds by name, they didn’t know if they were male or female. There’s simply no way to tell the sex from the outside, Long said. Then, for an experiment that required that information, Long had a veterinarian make a small incision to find out what kind of sex organs each bird had. Long and the other researchers had, out of force of habit, started calling some birds “him,” and others “her,” but when the results came in they found that they’d assumed the wrong sex for every bird except one.
If the researchers had such a hard time sexing the birds, how did the turkey vultures themselves do it? Perhaps—and Long reminded me that this was “just a crazy idea”—they were smelling each other’s legs to determine who was a male and who was a female. Maybe there is some revealingly fragrant hormone in turkey vulture feces, which they deliberately apply to their legs.
This doesn’t seem so crazy. Any woman who has ever walked into a heavily used men’s room can tell you that male urine smells different. Transgender people undergoing testosterone therapy to transition from female to male have noted the same thing. But Long’s turkey vulture hypothesis will remain a crazy idea until someone has the time and money to figure it out. Like so many other basic facts about turkey vultures, it’s a mystery tantalizingly close to resolution.
After a couple of beers, I’d exhausted Long’s well of facts. “We need more science,” he said with a shrug. And if anyone wants to study them, they are right outside. Just look up.
A not-so-secret part of me wants Josephine to grow up to be the sort of science whiz who might solve these vitally important mysteries, but turkey vulture–watching was pretty boring for her. I’d point one out and she would spot the bird, but after about a minute she’d ask, “When will it find a dead animal?”
Unless you are lucky enough to stumble upon a roost or a carcass, you aren’t likely to see more from a turkey vulture than endless circling. I love seeing them do that; I like to imagine they are sweeping calligraphy across the sky. Nonetheless, I don’t have enough patience to decode this script, and Josephine has even less. So I moved our bird-watching inside, where we found more exciting footage on the computer: A turkey vulture eating a fish, a raccoon, a flattened squirrel.
“Would you like some dead squirrel guts to eat?” I asked Josephine.
She twisted around in my lap and smiled at me. “Can we be a turkey vulture family?” she asked.
Sure, of course.
She slid to the floor and ran into the dining room, waving her arms. “Flap, flap, flap, glide!” she chanted. I followed her, doing my best impression of the terrifying turkey vulture hiss-scream. Josephine pointed toward the window seat: “Look, Papa Turkey Vulture, a dead squirrel! And a dead hamster!”
We ate them all, leaving only the bones.
Once upon a time, around the last ice age, there were many more large mammals in the Americas. There were mammoths, mastodons, three species of bison, giant sloths, and giant camels. Back then, there was a lot more dead meat around, and there were many more kinds of vultures to eat it: There are several extinct teratorns, as researchers named them, including one species with an eighteen-foot wingspan, and another (in South America) that weighed up to 175 pounds. Those big mammals went extinct (humans, or an asteroid, or some combination may have killed them), and when those meat sources disappeared, the vultures died out too. There are just three species left in North America: California condors, which are barely hanging on; black vultures inhabiting the southeastern United States and Mexico; and turkey vultures, which have been the most adept survivors. You’ll see them everywhere from Patagonia to Alaska. They had stayed away from the far north, but as climate change warms the world there are reports from Inuit people in northern Nunavut of “bald ravens,” which have turned out to be a new (and apt) name for turkey vultures.
Those birds not only adapt well to change, they seem to thrive on it. When white people wiped out the buffalo, turkey vultures transitioned to feeding on dead farm animals and scraps from slaughterhouses. With the inventions of the automobile and the modern landfill, turkey vultures expertly flexed to exploit these new food sources.
Their strategy for survival is travel light. Though they look big, their body mass is low: They weigh only three to six pounds. They have hardly any fat reserves. When gliding during the day, they burn barely any energy. If they are low on calories they go into a state of torpor at night, their body temperature and metabolism plummeting, their heart rate and digestion slowing down. They aren’t muscular and fast like hawks, and they don’t have a cushion of fat to see them through hard times like ducks do. Instead, they’ve thrived for thousands of years by carrying as little baggage as possible. These introverts of the avian world, so lacking in social graces, have no use for excess or flamboyancy. And so we ignore them. Watch turkey vultures and they’ll show you how the invisible currents of air cascade through the sky, and where some other unseen animal has recently met its end. But mostly, turkey vultures remain a symbol of mystery. When the world surrounding the pattern of work, sleep, and commute starts to feel desperately straightforward and lacking in mystery, just look up at the bird kiting a clean line through the sky and remind yourself: There goes one of the great enigmas of the natural world.