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FIELD GUIDE

Ecological services, courtesy of your local vultures

A turkey vulture, which gets its name from its red head, in Barre.
A turkey vulture, which gets its name from its red head, in Barre.Richard Johnson/Mass Audubon/Mass Audubon

Walking through a pine grove north of Boston a few weeks ago, I was startled when a large, black bird came flapping through the forest canopy and landed on a branch about 50 feet away. Its wingspan looked to be about 5 feet or more, and at first I thought it was a big hawk. As I crept closer and got a better look, I realized it was a vulture.

We stared at each other for several minutes — me looking curiously up at the vulture, and the vulture looking nervously down at me. As I moved closer to take a photo with my cellphone, the big bird took flight and landed in another tree a little farther away. I could see some pink color on its head, which told me it was a turkey vulture. I snapped a picture of this unexpected visitor, and continued walking.

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The first time I saw a vulture in the Boston suburbs was about 10 years ago. Since then I’ve seen them more frequently, usually circling above roadways, probably searching for dead animals to eat.

The Mass Audubon website says turkey vultures used to be rare in Massachusetts, but in recent decades they’ve expanded their range northward, with the first confirmed breeding pair being observed in the state in 1954.

“It is postulated that the expansion in the turkey vultures’ range in the late ’50s and ’60s was due to the increase in the white-tailed deer population, as well as the banning of DDT,” said Joan Walsh, the Bertrand Chair of Natural History and Field Ornithology at Mass Audubon.

Vultures feed on dead animals, and more deer would likely mean more food for vultures, either through road kill, deer dying naturally, or being killed by hunters, Walsh explained.

DDT was a widely used pesticide that caused the thinning and breaking of some birds’ egg shells, such as birds of prey. Once it was banned, populations of the affected birds rebounded.

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Walsh also speculated that mild winters in recent years might have contributed to the northward expansion of the vultures’ range. She said they tend to migrate south in the winter, but a few may stick around if it’s a mild winter.

Black vultures are smaller than turkey vultures.
Black vultures are smaller than turkey vultures.Mass Audubon/Richard Johnson

Another species, the black vulture — primarily a southern species — started showing up in Massachusetts over the past 30 years, said Walsh.

Turkey vultures, which are more common than black vultures, get their name from their red-colored heads, which resemble turkeys, said Walsh. Black vultures have black heads. Turkey vultures, with a wingspan as long as 6 feet — also are a little bigger than black vultures.

“Turkey vultures hold their wings in a V-shape when they soar, and kind of teeter and wobble,” Walsh said. “They look like they’re drunkenly flying along. Black vultures not as much.”

Walsh said vultures like to nest in dark, dilapidated abandoned buildings, such as old barns. In natural settings they nest in dark, hollow logs, and caves-in cliffs, but they don’t make nests. Instead, they just lay their eggs on a flat surface.

She said they have one to two chicks, which the adults feed by regurgitating food from a special throat pouch.

Walsh said adult vultures have few natural enemies, and are most vulnerable as small chicks. She said coyotes or other predators could try to eat the chicks if they found them, but young vultures are pretty good at defending themselves. She said they will hiss loudly at prospective predators, and if that doesn’t work they try projectile vomiting.

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“If you frighten them, they will vomit at you,” Walsh said. “It’s one of the most disgusting animal ejections that you could come upon.”

Like most vultures, turkey and black vultures have bare heads and scaly skin. This could be for thermoregulation, helping the birds to cool off, said Walsh. But given vultures’ feeding habits — eating dead animals — feathers might get dirty and contaminated, so it’s possible bare heads help maintain vulture hygiene.

“If you stick your head inside of dead things, you don’t want a lot of feathers,” said Walsh.

Vultures locate dead flesh by scent and sight.

“And they’re really good at it,” Walsh said. “They’re also good at finding other vultures, which can lead them to carcasses. They share large carcasses.”

An article on the Smithsonian website says turkey vultures have an extraordinary sense of smell, and can locate carrion by odor, while black vultures rely more on locating dead animals by sight. Even though both species have about equally good eyesight, the turkey vulture’s better sense of smell allows it to detect dead animals in wooded areas, where black vultures aren’t able to see through the forest canopy.

Vultures in the United States, Canada, and Mexico are protected by the Migratory Bird Treaty Act, according to Walsh, but humans still remain their greatest threat, through accidental or outright killing, and through direct or secondary poisoning.

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The third, and largest, vulture species in the United States, is the California condor, which has a wingspan of up to 10 feet. It almost went extinct in the 1980s, said Walsh, but is now recovering through a captive breeding and release program.

Vultures provide important ecosystem services, said Walsh, as a lot of animal carcasses are cleaned up by these birds.

“If your business is dead stuff, your business is often booming,” Walsh said.

But, vultures also occasionally get hit by cars when feeding on road kill, she added.

“If you see vultures on a carcass on the highway, slow down and give them a break,” Walsh said.

The California condor, the largest vulture species in the United States, almost went extinct in the 1980s.
The California condor, the largest vulture species in the United States, almost went extinct in the 1980s.Craig Gibson
Turkey vultures on seal carcass at Plum Island in 2014.
Turkey vultures on seal carcass at Plum Island in 2014. Richard Johnson/Mass Audubon/Mass Audubon

Don Lyman is a biologist, freelance science journalist, and hospital pharmacist who lives north of Boston. Send your questions about nature and wildlife in the suburbs to donlymannature@gmail.com.