On July 22, 1997, Gonzo the Black Vulture stepped timidly onto northern soil for the first time at the Trailside Museums and Zoo at Bear Mountain State Park in the Hudson Valley. Born five years earlier at the Memphis Zoo, and later transferred to the Nashville Zoo, where he served as and education ambassador, Gonzo had made a northbound journey many members of his species would later take.
Early on in his career, Gonzo had developed a significant droop in his left wing, prompting surgery for a partial amputation to aid in his mobility. During his surgery, veterinarians discovered that Gonzo also suffered an irregular heartbeat. While it would be an early retirement from commercial zoo life, Gonzo would not be arriving alone in New York’s strange and unfamiliar landscape.
Like Gonzo himself, black vultures are historically southerners. They are a neotropical species ranging from South America to Virginia, which remained the case up to the mid-20th century. However, beginning in the 1980’s and increasingly ever since, black vultures have been engaging in a northward expansion.
Sixteen years prior to Gonzo’s arrival at Trailside, the first ever black vulture was recorded in New York state at Minnewaska State Park Preserve on November 1, 1981 by Dan Smiley, a resident naturalist at the nearby Mohonk Preserve. In 1997, the same year as Gonzo’s arrival, the first black vulture “nest” was recorded nearby on the eastern side of Bonticou Crag in Ulster County by Joe Bridges, a research associate with the Mohonk Preserve. The term “nest” is to be taken lightly, as black vultures aren’t much for creature comforts. Like all new world vulture species, black vultures forego building nests instead opting for hard-to-reach rocky crags and recesses in caves, hollow logs, brush piles, thickets, and abandoned buildings to lay their clutch of eggs.
For Gonzo’s first years at Trailside, his neighbors outside his enclosure would consist primarily of his slightly larger and keen-smelling counterpart, the turkey vulture, which was the dominant vulture species in the Hudson Highlands at the time. Black vultures such as Gonzo lack the turkey vulture’s sense of smell, instead relying their sharp eyesight while coasting thermals to forage for meals. Unable to smell carrion, black vultures have adapted a new strategy, relying instead on turkey vultures to do the work for them. To find food, all black vultures need to do is keep an eye on the lower-soaring turkey vultures. Once the turkey vulture descends, the black vulture follows close behind.
How to tell a black vulture from a turkey vulture
Since his early days at Trailside, Gonzo bore witness to a population boom in New York of his species, a black vulture golden age. The latest large-scale survey of New York birds was performed during 2000 to 2005, splitting the state into 5,000 geographic blocks. It confirmed black vulture nests in five blocks and reported suspected nests in 100; a significant increase since the last survey, performed during 1980 to 1985, which reported no found or suspected nests. Since then, its safe to say that the population has continued to increase as evidenced on local Christmas Bird Counts and the community science site eBird.org.
As to why the black vultures have taken up this avian manifest destiny to spread into New York, we are left only to speculate. Climate change may be a driving factor, turning New York’s colder climate into something milder and more habitable for black vultures. However, the black vulture’s range has shifted northward only along the eastern seaboard from Virginia, and along the Hudson River north to the St. Lawrence, with little change in the Midwest.
Other possible causes include an increase in deer and other mammal populations, and vehicle traffic, leading to increased food availability from roadkill, and greater tolerance of the species and increased protection under the federal Migratory Bird Treaty Act.
Despite being called “vultures”, black vultures and other new world species bear little similarity to old world species. Their common characteristics are a result of convergent evolution, or traits selected for a similar lifestyle. Both share bald featherless heads, perfect for rooting around in carcasses without ruffling any feathers. Both share similar circular flight patterns, utilizing the energy saving tactic of coasting on thermals. And both share the same highly corrosive digestive system; the PH of a black vulture’s stomach acid rests just above 0, akin to car battery acid and nearly 100 times as concentrated as human stomach acid.
Black vultures are instead more closely related to storks with whom they share an interesting, yet effective means of thermoregulation[1]. If a warming climate is the culprit behind the black vulture’s expansion, they will, without a doubt, continue to thrive in warmer climates thanks to urohidrosis; or the habit in some birds of defecating onto the scaly portion of the legs as a cooling method, using evaporative cooling of the fluids.
[1] Thermoregulation is the ability of an organism to keep its body temperature within certain boundaries, even when the surrounding temperatures is very different
Additionally, keeping in mind that a black vulture’s stomach acid is highly acidic, they produce a sterile excrement which cleanses their feet of bacteria and parasites, which may accumulate due to their scavenger lifestyle. Two birds with one stone, if you will
Black vultures will also simultaneously thermoregulate and sanitize through the process of sunbathing. Often observed with wings out and backs to the sun, these birds are warming their bodies while utilizing the UV radiation from sunlight to kill bacteria and parasites on their feathers.
As adults, black vultures experience few predators. Their main threat comes in the form of nest predation either by raccoons or foxes. Despite their relative safety, vultures still maintain a gruesome defense mechanism against predation; defensive vomiting. Utilizing their stomach acid once more, black vultures are able to produce a foul smelling and corrosive vomit that acts as a deterrent and mace for predators.
In addition to clever adaptations, black vultures themselves are undoubtedly intelligent birds, this trait being readily observable in Gonzo and other captive black vultures. Gonzo observed and interacted with the world around him with great curiosity. Behind his soulful brown eyes, there was a spectacular presence, a timid and gentle personality with an almost irrefutable perception and understanding.
The social intelligence hypothesis posits that human “intelligence” has evolved in order to adapt to complex interpersonal relations and is generally accepted in the current theory of evolution. It is believed that as the size of the group increases, it becomes necessary to adapt to more complex social relationships within the group, driving the selective pressures for increased neocortex size. Black vultures are not exempt from this theory, belonging to flocks largely composed of family units and roosting in large masses in the evening.
At Trailside, where the black vultures seemed to have designated the bear exhibit as their daytime roost, their community engagements can be observed through mutual preening, playful chasing, food sharing, and the occasional scuffle. But perhaps the best example of their sociality was seen with Gonzo.
Confined to his exhibit, Gonzo began receiving vulture visitors, and over the years they grew in number to the point which on any given day a sizeable flock of wild black vultures could be seen mingling with Gonzo. Perhaps they were assessing the mystery as to why this member of their species was captive, putting their bald little heads together in a sort of vulture think-tank, or perhaps, lacking his own flock, the wild vultures assimilated him into their own.
Keepers at Trailside have observed on numerous occasions, the passing of food between cage bars to the flock; perhaps, an altruistic sharing of of a captive bird’s bounty. Food sharing in wild vultures is typically only observed within members of the same family. Perhaps Gonzo viewed this flock as a sort of family. Between shared mice and fish, did the vultures swap tales of harsh winters, open skies, and a northbound journey? Voiceless secrets told hushed through throats lacking a syrinx[2]
[2] The syrinx is the lower larynx or voice organ in birds, situated at or near the junction of the trachea and bronchi and well developed in songbirds
Because Black vultures lack the organ responsible for birdsong in many species, their vocal repertoire consists mainly of huffs, grunts, and hisses. Click here to hear a recording of a black vulture from the The Cornell Lab of Ornithology Macaulay Library.
On the black vulture’s sociability, Charles Darwin wrote:
“These vultures certainly may be called gregarious, for they seem to have pleasure in society, and are not solely brought together by the attraction of a common prey. On a fine day a flock may often be observed at a great height, each bird wheeling round and round without closing its wings, in the most graceful evolutions. This is clearly performed for the mere pleasure of the exercise, or perhaps is connected with their matrimonial alliances.”
It certainly does appear that black vultures perform many activities through the sheer pleasure the action brings. Play is widely regarded as a hallmark of intelligence in birds, observable in both crows and ravens. It is an activity which helps an individual gain information regarding its environment; and play in many forms can be observed in the vultures of Bear Mountain. In the bear den and along the zoo trail, black vultures can be seen taking turns chasing each other, tossing about hay, playing with sticks and feathers, ripping apart paper bags, tugging on the mesh of exhibits.
Play is also one of the reasons many Hudson Valley residents are at odds with vultures. In their exploration of this world, it turns out black vultures can be quite destructive. Their favorite pastimes including tearing rubber from windshield wipers, and shingles from roofs.
Several years ago the Bear Mountain Inn experienced nearly $10,000 in roofing damage by black vultures and, as of 2017, black vultures are estimated to have cause nearly $75,000 in damages statewide. Much like teenagers, if you have enough black vultures in one place without enough to do, they’re bound to get up to trouble. As a consequence, many Hudson Valley businesses and residents are now flying in face of the Migratory Bird Treaty Act and federal law, taking up arms against the vultures. Several methods of deterrence include lasers, sprinklers, pyrotechnics, trapping and effigies; but with a population on the rise, conflict with humans is only more likely to increase.
On the other side of the coin, black vultures are a necessary asset to our ecosystem, serving as “nature’s cleanup crew” feeding on the dead and diseased other carnivores wouldn’t dare venture near, their stomach acid allowing them to safely digest putrid carcasses infected with rabies, botulinum toxin, hog cholera bacteria, and anthrax bacteria that would be lethal to other scavengers. Their work halts the further transmission of these diseases between humans and other wildlife, a role which, in the age of a zoonotic pandemic like COVID-19, is paramount.
For all those still at odds with the black vulture, Gonzo served as a shining exemplar of his species positive qualities, and magnificent beauty, connecting the black vulture in the minds of many to a handsome bird, with a quiet, yet inquisitive personality.
Gonzo passed away at Trailside on Tuesday, June 22, 2021 at 29 ½ years old. While longevity records for black vultures are scarce, Gonzo may have well been one of the oldest specimens in captivity. He leaves behind the legacy of being one of New York’s pioneer black vultures, who instilled a passion and understanding for his species in many visitors.
Gonzo is survived by his flock, a family he made all his own, the wild vultures of Trailside. Months later, the occasional solemn vulture could still be seen idling outside what was once his aviary, wearing all black feathers, dressed as if for mourning.
Post and photographs by Malerie Muratori, Student Conservation Association intern at Trailside Zoo.
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