Tuesday, July 28, 2020

Turkey Vultures close loop in circle of life

Every creature plays a role in maintaining the balance in nature. Turkey vultures in particular have an important job. They are “carrion” eaters, which means they scavenge the remains of dead animals.

We often see them overhead, their broad v-shaped, five to six foot wingspan teetering effortlessly from side-to-side on rising thermals, like a kite in a gentle breeze, using their keen eyesight and highly developed sense of smell to locate the carcasses of recently deceased animals. 

Contrary to popular belief, circling vultures are not always looking for a meal, but rather travel without flapping their wings, riding thermals up, before gliding in a gradual descent, to where a second thermal is detected, then repeating the process. In this manner, turkey vultures can fly without much flapping of the wings for up to six hours. A group of circling vultures, called a “kettle” (bubbles rising in boiling water?), is as often an indication as to where rising warm thermals are located, as to where an animal’s carcass lies.

Also contrary to popular belief, vultures are extremely shy and wary of people, don’t follow dying animals, and will occasionally eat shoreline insects and vegetation. I’ve seen one of our turkey vultures, Ike, eat pumpkin and squash placed in the enclosure he shared with Lenoire, the Raven.

Large groups of vultures, called “venues,” are often seen roosting on the bare limbs of dead trees, spreading their wings to dry them after rain, or absorbing heat, baking off the bacteria picked up during days spent with their heads in, and their bodies moving around, carcasses. Or, we may see them circling high over an area where the gases, most notably ethyl mercaptan, emitting from decaying carcasses, (and used to give odor to odorless and potentially dangerous gases like propane),  signal the presence of food. 

Similar species

Turkey vultures are related to black vultures, yellow-headed vultures and condors, and received their name, by the resemblance of their feather free heads and dark-feathered bodies to wild turkeys. Turkey vultures are also more closely related to storks and ibises than raptors.

Slightly larger than their more southerly cousin, the black vulture, which, with warming climate, is beginning to show up in the southern Adirondacks, the turkey vulture rarely kills its own prey, preferring to eat road kill, fish which have washed up on shore or any deceased creature whose carcass has not begun to putrefy. Yes, there are actually carcasses that are too putrid even for vultures, and attract a whole different group of scavengers! Also, vultures prefer the carcasses of herbivorous animals over those of carnivores.

One way in which raptors differ from turkey vultures is that raptors have a very limited sense of smell, which is why Great Horned Owls, for example, eat skunks. Smells are processed by the olfactory lobe of the brain, which is larger than normal in turkey vultures. Old world vultures have no sense of smell, but, like turkey vultures, have very acute eyesight, which they use to locate carcasses. 

This is an example of convergent evolution, wherein two creatures who are unrelated, but evolve in environments which are distant, but share similar opportunities, i.e., large dead animals, end up filling essentially the same role, and develop similar attributes which make them come to resemble one another. The African vulture lives in an open area where it is easy to spot carrion from the air, while the turkey vulture lives in areas which include dense canopy, so smell becomes a key advantage. Since a vulture spends so much of its life with its head inside the carcass of an animal, natural selection has gradually removed the feathers from the head, as feathers would accumulate bacteria and bits of putrefying flesh. The merely aesthetic tradeoff is the vulture’s ghoulish appearance. 

Vultures have no syrinx, the vocal organ found in birds, so their vocalizations are limited to hisses and grunts. Also in distinction to raptors, turkey vultures have weak, almost flat feet, which can be used to stand on carrion, to keep it from shifting as they pick and tear at it with their short, ivory-colored beaks. As graceful as they appear when circling or gliding, the turkey vulture is quite awkward on the ground, alternately hopping and walking, and takeoffs are clumsy and laborious. A surprised vulture defends itself by vomiting up a noxious stew of undigested material, often emptying its crop, and often making it lighter to enable takeoff, while its pursuer may be distracted by the free meal offered by the vomited material.

Fun facts

  • Mature vultures have few natural enemies, but immature vultures may be taken by eagles and great horned owls.
  • Vultures spray their urea on their legs, and the evaporation of the fluids enables cooling, while the uric acids in their waste kill the bacteria which accumulates on their feet and legs.
  • Reproduction: Two eggs are laid on the ground in a protected, scratched out depression, like on a  a cliff, in a cave, or in a hollow tree or abandoned barn, in April or May.
  • Incubation lasts 38 to 41 days, and fledges leave the nest about 70 to 80 days after hatching.
  • Vultures only have one brood per year.
  • Vultures live about 16 years in the wild, and about 20 in captivity.
  • Turkey vultures are protected under the International Migratory bird Treaty. Ike came to us from the Wild Center in Tupper Lake. Ike had to have a wing amputated at the wrist after being struck by a car. Turkey vultures are migrators, which is why Ike has a heat lamp in his “cave.”

In closing, I’ll leave you with a passage from Robinson Jeffers, environmental poet from the 40s and 50s.

I had walked since dawn and lay down to rest on a bare hillside
Above the ocean. I saw through half-shut eyelids a vulture wheeling
high up in heaven,
And presently it passed again, but lower and nearer, its orbit
narrowing,
I understood then
That I was under inspection. I lay death-still and heard the flight-
feathers
Whistle above me and make their circle and come nearer.
I could see the naked red head between the great wings
Bear downward staring. I said, ‘My dear bird, we are wasting time
here.
These old bones will still work; they are not for you.’ But how
beautiful
he looked, gliding down
On those great sails; how beautiful he looked, veering away in the
sea-light
over the precipice. I tell you solemnly
That I was sorry to have disappointed him. To be eaten by that beak and
become part of him, to share those wings and those eyes–
What a sublime end of one’s body, what an enskyment; what a life
after death.

Top photo of turkey vulture by Brenda Dadds Woodward. The remaining photos by Steve Hall and pastel by Wendy Hall, all courtesy of Adirondack Wildlife Refuge.

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Steve Hall

Steve and Wendy Hall run the Adirondack Wildlife Refuge and Rehab Center in Wilmington. They've been rehabbing and releasing wild animals for over 45 years, specialize in predators, keep wolves as the cornerstone of their educational program, and have lived in the Adirondacks for the past 20 years. The Adirondack Wildlife Refuge became a non-profit about 10 years ago.

Visit www.AdirondackWildlife.org to learn more.




17 Responses

  1. Boreas says:

    Great article!

  2. Bobbi says:

    Very informative and interesting. I saw once three turkey vultures lined up on the top of the barn spread eagle and wondered what they were doing. It was quite a sight. Thank you for all the facts and fun tidbits!

  3. Charlie S says:

    “Since a vulture spends so much of its life with its head inside the carcass of an animal, natural selection has gradually removed the feathers from the head, as feathers would accumulate bacteria and bits of putrefying flesh.”

    “A surprised vulture defends itself by vomiting up a noxious stew of undigested material, often emptying its crop, and often making it lighter to enable takeoff, while its pursuer may be distracted by the free meal offered by the vomited material.”

    Very interesting life is…the individuality in species, survival instinct, all of the interesting characteristics. The beauty!

  4. Jim Fox says:

    Disgustingly fascinating!

  5. Ed Burke says:

    Very spectacular birds, saw a roost of about 18 in a tree near South Bay once. Saw a black vulture at Minnewaska State Park then read up to confirm and it said they sometimes hang around with turkey vultures because their eyesight isn’t too keen and it helps them find food. Favorite Far Side cartoon has always been the vulture at The Carrion Cafe complaining to the waiter that his meal wasn’t spoiled.

    • Ed from Hastings and new Zealand? Hi Ed. Yes, black vultures, probably my next article, are moving north with warming climate. We used to hike Minnewaska when we lived in Putnam County. Beautiful Park.

      • Boreas says:

        Saw a Black Vulture in Peru, NY a week or so ago with a Turkey Vulture. Only a handful of sightings in Clinton County. Odd time of year – they may be starting to breed up here.

  6. Suzanne says:

    Wonderful article. Wendy Hall’s pastel illustration is particularly beautiful.

  7. Philip Terrie Phil Terrie says:

    Good read! Thanks. Twenty-five years ago, I did not see turkey vultures in the central Adks. Now I do. Was I just failing to notice them then, or have their numbers here increased?

    • Phil, we’ve lived here twenty years, and I believe their numbers have increased all over. I spent many Summers up here as a kid, and I believe I would have noticed turkey vultures, but have no memory of that. Having said that, black vultures, which I used to go see in the Everglades and Texas gulf coast, have been seen as far north as Saratoga, and we’ve rehabbed a few. Steve

      • Suzanne says:

        Growing up in Columbia County and spending summers in Keene Valley, I never remember seeing vultures. (I wouldn’t recognise a black vulture from a turkey vulture because they fly so high up–I need better binoculars!) Eagles were rare, as were herons, and it was always exciting to see one. Now both are flourishing along the Hudson. I know of five eagle nests between Rensselaer and Rhinebeck and frequently see the eagles fishing on the River. I gave up counting the herons because there are so many. Nature, given a chance, can renew itself. One must only hope that the current administration’s deregulation of environmental rules will be a thing of the past after the election.

        • Boreas says:

          Suzanne,

          Good binoculars are always a plus, but they are pretty easy to tell apart if you know what a TV looks like – deep dihedral angle in the wings when soaring and long light underwent patches running most of the length. A Black Vulture at first glance looks more like a very dark hawk (buteo) with relatively shorter/broader wings with light patches on the tips, minimal dihedral when soaring, and more of a head. They are also smaller overall.

  8. Ritaclare Streb says:

    Thank you. I enjoyed this so much. Here in Rochester we have eagles and turkey vultures!.Quite often you can see eagles flying over the Genesee river. Last summer I saw a group of turkey vultures flying round and round over the shore of Lake Ontario. I’m thinking they were looking for fish carcasses. I’ve seen them feeding on them on the shore in the past.

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