Vulture Days

Turkey vulture in flight over Brush Mountain

Turkey vulture in flight over Brush Mountain

Last September once again I missed International Vulture Awareness Day. That was on September 7 and my husband Bruce and I were celebrating our fiftieth wedding anniversary in the province of Quebec. Specifically, we were sitting six feet away from the largest common gannet colony in the Western hemisphere, watching them fighting, mating, tending young, and diving for food.

If only watching turkey vulture behavior on our mountain was as easy. Of course, I do see them sailing up and down Sapsucker Ridge most days from early March, when they return from their winter quarters, until mid-November when they are off again. We think we may have had a pair nesting somewhere on the talus slope because several years ago our son Dave saw an almost grown youngster sitting on the rocks.

Then, in the spring of 2012, our caretaker Paula Scott reported seeing a turkey vulture sitting the entire day on top of the deserted and wrecked home our late former neighbor Margaret McHugh. Paula watched the bird from her own home that had been built farther up the hill and looks down at the old place.

According to researchers, old, deserted homes and other buildings are favorite nesting places for turkey vultures. I was hopeful that I would finally be able to watch from Paula’s home (a natural blind) the domestic affairs of a pair of turkey vultures.

But it was not to be. Paula never saw any further sign of vultures near the house, and it was too dilapidated for us to climb up to the attic and check it out. Probably the close proximity of the Scotts’ home had discouraged the vultures if, indeed, they had been interested in nesting in the old house.

Maybe they nested in the talus slope instead or in the crevice of one of many fallen trees on our property. I only know that on September 24, a clear, breezy day, I was walking down First Field when I spotted a vulture sitting on a power pole at the base of Sapsucker Ridge. At first I thought it was a black vulture because it had a gray head. But so do immature turkey vultures and this one had a long tail, not the short one of a black vulture. Then a mature turkey vulture followed by a second and a third one soared close to the power pole vulture as if showing the youngster how to ride the wind as they do.

Juvenile turkey vulture grooming itself at the edge of a talus slope

Juvenile turkey vulture grooming itself at the edge of a talus slope

But the youngster paid no attention to the soaring vultures. Instead, it groomed itself. It also ignored me as I edged closer and closer. Even when I walked beneath the pole, shouted and clapped my hands, it didn’t budge. It didn’t even look down at me. Only an immature would be so oblivious to a human. I studied it for a long time, but it never did fly off. However, watching it had given me the chance to celebrate International Vulture Awareness Day a little late.

Even though our turkey vultures are the most widely distributed and abundant of all vulture species worldwide, ranging from southern Canada to the southern tip of South America and on large and small islands from Cuba and Puerto Rico to the sub-Antarctic Falkland Islands, many species have rapidly dwindling populations. For instance, three of south Asia’s vulture species lost 99 percent of their population in 25 years due to a veterinarian drug used on livestock that is toxic to vultures and five African species are gravely threatened by accidental and purposeful poisoning. Since most people don’t like vultures, they only learn after they lose them how invaluable they are in cleaning up dead creatures.

Hawk Mountain Sanctuary researchers have been studying turkey vulture migration behavior since the spring of 2003 by radio-tagging some and surgically implanting a data logger in the bodies of others which records core body temperature and heart rate. They also wing-tagged dozens of them in an effort to learn more about the extent, causes and consequences of their annual migration.

According to their website, their goals in monitoring New World raptors are to “routinely monitor seasonal populations of New World vultures in North, Central and South America, prevent catastrophic population declines by sharing learned information with conservation partners, and use black and turkey vultures as environmental sentinels of ecological change and environmental contamination, including climate change and heavy metal contamination..”

They have discovered that our subspecies of turkey vulture Cathartes aura septentrionalis is a partial migrant to as far south as Texas and southern Florida, although in February of 2010 Dr. Keith L. Bildstein and Lauriane Streit drove down the Delmarva Peninsula from Milford, Delaware to the Chesapeake Bay Bridge tunnel toll booth passing numerous chicken farms, each with its own flock of vultures, and called it “one of the biggest East Coast winter resorts for vultures.”

A longer drive along the coast found that there were more turkey vultures than black vultures, for example, on the Delmarva drive they counted 245 turkey vultures to 23 black vultures. But on counts in the Appalachian Mountain from northern West Virginia to North Carolina and Tennessee there were more black vultures than turkey vultures.

Juvenile turkey vulture cleaning its beak on a rock

Cleaning its beak (?) on the rock

Bildstein wrote the turkey vulture section in the Second Atlas of Breeding Birds in Pennsylvania and reflects on the difficulty of finding turkey vulture nests, saying that up to 70 percent of a local population may not breed. Nevertheless, he has good news about their numbers. They have expanded in the Appalachian Plateau region of Pennsylvania from their former range in the more southerly part of the state and have shown a 13 percent increase in breeding blocks from those reported in the first Pennsylvania breeding bird atlas project back in 1983-89. The Breeding Bird Survey also reported a 50 percent increase in turkey vultures between 1966 and 2009. Migration hawk watches throughout the state similarly have observed an increase in turkey vulture migrants.

Bildstein believes that the increase is due to several factors: the increasing numbers of wildlife including white-tailed deer that are killed on highways and decreased persecution of them by humans. While most Pennsylvanians may not care that much for turkey vultures, apparently they appreciate their role as nature’s scavengers, cleaning up not only dead wild animals but domestic ones as well.

Using their keen sense of smell to help locate food, they feed on carrion without getting much gore on their naked heads. No doubt, this reduces their exposure to bacteria, parasites, and disease. Still, in his “Vulture Chronicles,” an absolutely delightful ongoing account on the Hawk Mountain Sanctuary website by Bildstein and other researchers of their work with vultures, not only in the Western Hemisphere but in the Eastern one as well, he writes that they still are threatened by “high levels of toxic chemicals in human habitations (including human drugs in urban areas, and agricultural pesticides in farmlands)…” In addition, they often fly into transmission lines while searching for carrion with their heads pointed down. They may also crash into vehicles. Because they feast on dead and dying birds and human garage they are exposed to “veterinarian drugs and antibiotics that contaminate the carcasses of domestic livestock and heavy metals that contaminate our dumping grounds.” Those that feed on such food Bildstein calls “human-subsidized” vultures and cites several incidences in North and South America of turkey vultures zeroing in on humans at campgrounds and other places where they might get human leftover food.

That brings me to a poem by Hilaire Belloc written in 1897 for his book More Beasts for Worse Children which says:

The Vulture eats between his meals,
And that’s the reason why
He very, very, rarely feels
As well as you and I.

His eye is dull, his head is bald,
His neck is growing thinner.
Oh! What a lesson for us all
To only eat at dinner!!

Juvenile turkey vulture getting ready to head up into the roost tree

Getting ready to head up into the roost tree

All photos by Dave Bonta.

Nature’s Garbage Collectors

turkey vulture above First Field

A turkey vulture soars over First Field in Plummer's Hollow

Like residents of Hinckley, Ohio, who always welcome the first turkey vultures back on March 15, I too await the return of them in March and regard them as one of the first signs of spring.  Usually the day they appear here is windy, and they rock back and forth above First Field, their wings tilted in their distinctive V-shape, which enables them to soar and glide for hours without flapping their wings.

According to recent studies by raptor biologists at Hawk Mountain Sanctuary, most Pennsylvania turkey vultures have returned from Florida or Georgia, but others return from nearby southerly states.  Still others never leave the commonwealth, occupying roosts in southeastern and south central Pennsylvania counties.

Twenty years ago, in late January, I visited the large winter vulture roost at Gettysburg National Park. The center of vulture activity is focused on an area aptly nicknamed “the Valley of Death,” after the battle, although contrary to legend, the vultures did not first appear in the area to clean up the dead horses after the battle in 1863.  Turkey vultures were in the area long before then, and black vultures, previously living only south of the Mason-Dixon Line, didn’t emigrate there until the late 1930s or early 1940s.

Watching hundreds of vultures as they gradually entered the roost at night and vacated it at first light, was a memorable experience.  No wonder Jim and Shannon Lang of Tyrone were excited when vultures chose their 27-acre, wooded property as a seasonal roost in 2006.  Located on a hill above the wooded town park, with houses on side of them, their 1930s-era house and their pool were shrouded with trees that darkened their prospect.  Shortly after moving in, they cut down 25 large trees, and the next year the vultures arrived in March.  They hang out in the four acres of open woods around their house and garage and beyond their pool.

turkey vultures at Gettysburg by Henry McLin

Turkey vultures at Gettysburg by Henry McLin (Creative Commons BY-NC-ND licence)

“They seem to have three or four favorite trees,” Shannon says.  “I call those trees the Radisson.  When they are filled, they go to smaller trees — the Motel 6.”  Those trees are mostly oaks and conifers.  That habitat — partially open under a canopy of large trees to give the vultures room to move around in — is perfect for a vulture roost.  And in southern Pennsylvania, northern Maryland, and northeastern Virginia, according to a study, roost sites were closer to clearings, human residences, roads and permanent streams than roosts in other parts of the United States.  That perfectly describes the habitat of the Lang’s roost because there is a stream on their property and in the park below.

Shannon, who has a degree in wildlife biology, enjoys watching the vultures even though her neighbors think they are spooky and wonder why she doesn’t get rid of them.

“I think they’re fascinating,” she says.  “They add to the wildlife. I like to see them in the morning when,” she tells me, “they are off by 7:30 and back around 7:20 in the evening. You could almost set your watch by them.”

She adds that they are quiet and clean.  Her two sons collect the pellets the vultures cast below the trees, gagging them up while they lie in a horizontal position, their bodies hanging down and heads bobbing.

Shannon has even watched the vultures play.  Once, when their pool was still covered, a turkey vulture landed on it and using its beak, tried to roll a large ball that her sons had left on top of the cover up a slight incline.  Each time the ball rolled back down to the vulture and it tried again. Apparently, its antics kept the entire family entertained for quite a while.

A turkey vulture basks in the last rays of sun before going to roost above a rockslide on Brush Mountain

A turkey vulture basks in the last rays of sun before going to roost above a rockslide on Brush Mountain

The Lang’s roost is a seasonal one and is made up mostly of turkey vultures with a couple black vultures and has about 52 birds.  These communal roosts — winter, seasonal, or year-round — can range from a few birds to several thousand, although the largest are winter roosts because both residents and migrants occupy them.  The one at Gettysburg National Park has held as many as a thousand vultures and those in Florida more than 4,000.

Such roosts are probably used to escape predators, provide opportunities for various social interactions and supply meeting places for possible mates.  But surprisingly little is known about the life history of these common birds.  For instance, researchers believe they mate for life, but they aren’t certain. They also don’t know at what age turkey vultures mate for the first time, but they do suspect that less than half of most populations breed in a year.

Here in Pennsylvania, turkey vultures arrive in early to mid-March, and most eggs and nests are found between April 18 and May 14.  But turkey vultures are secretive nesters, and while researchers think they nest throughout the state, during the first Breeding Bird Atlasing, only one per cent of observations were those of nests.  That’s because the females usually lay their one to three, creamy-white, blotchy eggs in deep recesses such as caves, crevices, and ledges, in mammal burrows, cavities in banks, or in large, hollow logs. Once they find a good nesting area, they often reuse it for long periods.

A mated pair frequently sit together near their nest site for days or weeks before nesting and engage in what researchers call “Follow Flight, something I’ve observed over First Field, when one bird flies behind and above the leading bird, often twisting and turning just as the leader does.  Sometimes the trailing bird dives at the leading one, partially folding its wings and diving directly toward it while the leading bird twists sideways and drops and the trailing bird flies upward again, neither bird touching the other. Other displays, such as ritualized “dancing,” bill-gaping, and wing-spreading have also been observed by researchers before the birds mate on the ground, rocks, or in trees while nibbling or poking at each other’s naked, red heads.

After the female lays her second egg, she and her mate take turns incubating them. It takes between 38 and 40 days for the eggs to hatch young that are downy with naked faces, throats, and crop areas. The parents also take turns brooding them until they are two weeks old and feed the young by regurgitation. By 18 days of age, they are able to stand up and retreat into the recessed nest to escape predators.  They can also stomp their feet, hiss, and perform what ornithologists call “Scare Jump” or “Scare Rush,” when they lunge forward, their heads thrust upward, flap their wings, open their bills, and hiss in a bluff attack.  Such an attack was enough to turn my Uncle Cal permanently against “buzzards,” as he called them when he told me about crawling into a cave outside Pottstown when he was a teenager and meeting the “Scare Rush.”

T.V. chick on a nest in a hollow tree in Michigan, by David Allen

T.V. chick on a nest in a hollow tree in Michigan, by David Allen (Creative Commons BY-NC-SA)

Between 70 and 80 days of age, nestlings become fledglings, flying above the canopy, and leave the nest area for communal roosts when they are 12 weeks old, about the time in August when the Lang’s roost increases in size for a few weeks before the vultures are gone for another year.

Turkey vultures are unique among vulture species because they can smell as well as see their prey, which is why black vultures often follow turkey vultures to a carcass and then bully them away from it.  One early May day, as I approached the Far Field, I spotted a turkey vulture in a tree that spread and shook its wings but remained on its perch.  One of our turkey hunters had told me about a dead deer there.  Then, I noticed a second turkey vulture in the same tree while a third wheeled overhead. After a few minutes, the first vulture soared off.  Suddenly, a black vulture flew up from the ground, sat in a tree a short time, and flew back down on to the dead deer hidden in the grasses below. After picking at the carcass for a few minutes, it flew up to the remaining turkey vulture and chased it away.  Then it too flew off.  Although black vultures are a little smaller than turkey vultures, they always dominate them.

The scientific name for turkey vulture is Carthartes aura, which means “breezy purifier.”  As primarily scavengers, the pH of a vulture’s stomach acid is an incredibly corrosive zero, which allows them to eat rotting flesh that might contain anthrax or botulinum.  In addition, they use it as a weapon projectile, vomiting on any potential predator.  As if that weren’t disgusting enough, they also defecate on their legs because the high ammonia content of their feces, ornithologist David Bird says, probably “kills off potentially harmful microorganisms picked up while standing in and wading through rotting carcasses.”

Such food can most easily be found in a mixed farm and forest habitat such as we have in our area.  There they eat the carcasses of both wild and domestic carrion such as livestock, woodchucks, skunks, raccoons, opossums and deer.  In fact, turkey vultures only moved into Pennsylvania’s wooded mountains in the 1920s and 30s to feed on starved deer.  A study of turkey vulture pellets in North Carolina also found Bermuda grass, pieces of plastic sandwich bags, brown paper sacks, and polystyrene in them, which proved that turkey vultures clean up road kills.  Without them, we would have many dead critters around.

They also hang around landfills, as Keith Bildstein of Hawk Mountain Sanctuary and James Mandel of Cornell University discovered.  They spent 120 days in 2004 and 2005 watching turkey vultures from an unused hilltop at Waste Management, Inc. Landfill in Pen Argyl, Northampton County.  The 30 to 90 turkey vultures that fed there roosted at three nearby communal roosts.  Of those vultures, 10 to 15 stayed 90 to 210 minutes after the local sunset while turkey vultures that fed in nearby farmlands, woodlands, and suburban areas returned to their roosts no later than 30 minutes after sunset. Those vultures that remained at the landfill used hot air thermals caused by two methane venting sites to give them lifts to leave the landfill long after natural thermals had subsided for the night. However, landfill workers found turkey vulture carcasses at or near the base of the vents which suggests that the flares killed them by suffocation or scorching.

Turkey vultures with a roadkilled opossum

Turkey vultures with a roadkilled opossum in Missouri, by Auntie G (Creative Commons BY-NC-ND)

Bildstein and other raptor biologists at Hawk Mountain Sanctuary launched a long-term study of turkey vulture migration in 2003 to, in their words, “learn more about the extent, causes, and consequences of their annual journeys.” They put tiny radio tags monitored by satellite on 24 turkey vultures in order to study both their autumn and spring migrations. According to raptor biologist, David Barber, who is working on this study and recently spoke to our local Juniata Valley Audubon Society, four of eleven turkey vultures that he studied were migratory.  Those that migrated went to Florida and Georgia, but while some go to the same place every year, others seem to adjust to the weather.  They don’t always take the same route.  Some migrate along the coast.  Others go down the Appalachian spine. Pennsylvania birds take a month to migrate making many stopovers and waiting for the thermals to waft them south.  By implanting five vultures with heart-rate loggers, the researchers discovered that they don’t use very much energy to migrate.  The wind does all the work.

Today turkey vultures are a  continent-wide, common species, and Hawk Mountain scientists want them to remain so, unlike the incredible decline of Old World vultures in many parts of Africa and southern Asia, especially in India where an anti-inflammatory drug given to cows has caused kidney failure within 36 hours to vultures that have scavenged the bodies of cows containing the drug. The population fell from 40 million in the 1980s to a couple thousand today, “the most catastrophic decline of a raptor species anywhere,” Bildstein says.

Maybe we should all celebrate the second International Vulture Awareness Day next September 4. It grew from Vulture Awareness Days run by the Birds of Prey Working Group in South Africa and the Hawk Conservancy Trust in England.  I was also pleased to learn about the Turkey Vulture Society, a nonprofit scientific corporation whose “purpose is to promote scientific studies of the life habits and needs of the Turkey Vulture, to protect the vulture and its habitat, and to inform the public of the valuable and essential services this bird provides to mankind and to the environment.”

Turkey vultures heating up in the early morning sun by Linda Tanner

Turkey vultures heating up in the early morning sun by Linda Tanner (Creative Commons Attribution licence)

The two unattributed photos are by Dave Bonta. Click on any of the other photos to view at Flickr.