They can be kind of disgusting,” Wildlife Ecologist at City of Boulder Open Space and Mountain Parks Heather Swanson says with a laugh, before admitting, “I like them. They are cool.”
They are cool, but they’re also gross, intriguing and a key piece of the puzzle that is Boulder’s ecology.
People don’t know a lot about turkey vultures. They’re amazing flyers, and they hang out in packs, roosting in colonies and migrating together. They’re ugly and they even have a sense of smell.
Vultures, particularly the turkey vultures that have claimed a local west end neighborhood as their turf, are the misunderstood cousins of the avian world. According to Swanson, not a lot is known about them.
“It’s pretty interesting for how common they are that there hasn’t been a lot of study,” she says.
But, like some sort of freak sideshow at a circus of ill repute, they’ve drawn the attention of some biologists and we do know a few things.
First of all, vultures like to hang out together. This is clearly evident to their neighbors.
“They’ve been here at least 20 years,” says long-time local Bob Lundeen of a colony that roosts in the shadows of Flagstaff mountain.
The vultures “show up all at the same time, each year,” he says. “All of a sudden they’re here.”
“They come back the first week of April,” adds another neighborhood resident, Lynn Morgan. “The same week every year.”
Morgan laughs and adds, “We have snowy weather in April and I still see them. They huddle up there.”
The sudden arrival as well as the equally sudden departure is typical of migratory species.
“They travel widely across the Americas,” says Swanson. “We have them during the summer and they go to central and south America in our winter.”
Boulder’s colony — or “committee” of vultures — is part of a five-subspecies subgrouping of turkey vultures scattered across the Americas. The subspecies is often confused with other vultures, including black vultures, a notorious bird that has been known to attack in packs, killing newborn cattle.
In the big picture, vultures are everywhere. They are comprised of two groups, Old World vultures and New World vultures. You can watch them fly almost anyplace except the colds of the Antarctic and, surprisingly, Australia, a continent that would seem well-suited for the birds. Both groups evolved separately but at the same time, a convergent process that gave birth to Boulder’s turkey vultures as well as other New World vulture species such as condors and king vultures. New World vultures are widespread, ranging from the
Falklands to Kansas to Costa Rica, while Old World vultures are found in Europe and Africa and include the Rüppell’s vulture, a species that holds the record for the highest flight in the world, having been documented soaring 36,000 feet above sea level.
Boulder’s turkey vultures are graceful fliers, but they don’t go quite that high. Weighing up to four pounds, their size comes from their wings. With wingspans up to six feet across, the birds are able to surf thermals with a minimum of effort.
Regardless of where turkey vultures fly or the trees that they call home, they all eat the same thing: dead meat. Turkey vultures have an acute sense of smell, a trait that comes in handy when your favorite meal consists of rotting flesh. Turkey vultures are some of a handful of birds with this sense, and that, along with highly developed olfactory lobes in their brains, allow them to home in on the sent of ethyl mercaptan, a gas produced by the beginning of decay in dead animals. This sense of smell is so precise that other vulture species, which don’t have such refined nostrils, such as American vultures or king vultures, will follow turkey vultures to find food.
The ick factor of turkey vultures is enhanced by other traits. The primary form of defense for a turkey vulture is to vomit semidigested meat at any threat — it’s a form of chemical warfare that ensures there are few predators that eat the birds.
In Boulder’s open space, turkey vultures act as the de facto garbage men, cleaning up the landscape.
“We don’t see a lot of dead things,” says Swanson. “As scavengers go, they’re pretty effective.”
The birds aren’t too picky, according to Swanson. Roadkill or a mountain lion kill after the large predator is done work fine, she says. As does the carnage after a farmer mows a hay field, when small rodents such as mice and prairie dogs don’t get out of the way in time.
While their ability to take advantage of human activity, scavenging on road kill or cleaning up a freshly mowed field, makes turkey vultures highly adaptable to humans, their presence also is an indicator of the overall health of the ecosystem, says Swanson.
“Turkey vultures are a key in nutrient cycling. They are part of the whole fabric of how things work,” says Swanson. “This is an important thing. When you have larger animals die, those larger scavengers are important. And if there are not healthy populations of wildlife nearby, there won’t be things to scavenge on.
“Roadkill adds to the food base,” Swanson adds. “But vultures will move in on kills after the large predator is done, or they’ll eat small carrion, rabbits, prairie dogs and mice.”
Because of this diet, they’ve got some pretty interesting habits.
“They urinate on their legs to sterilize the skin,” Swanson says and laughs. “And the naked head, the purpose is to keep from getting rotting meat stuck in the feathers. They are kind of stinky.”
“They are kinda creepy,” says Morgan. “But they are very interesting to observe first thing in the morning, stretch their wings out and watch the air wake up.”
“They are fascinating,” adds Lundeen, who admits that he likes watching them come home every evening the best.
“They spiral down into the trees without even flapping,” he says. “It is the most impressive thing.”