Bad at Goodbyes

Rough Transcript

Intro 00:05

Welcome to Bad at Goodbyes.

On today’s show we consider the Slender-billed Vulture.

Species Information 02:05

The Slender-billed Vulture is a critically endangered avian raptor, a bird of prey, native to South and Southeast Asia, specifically Nepal, India, Bangladesh, Myanmar, Cambodia, and Laos. Its scientific name is Gyps tenuirostris and it was first described in 1844.

 

Description

The Slender-billed Vulture is a medium-sized vulture, about 3 feet in length, weighing roughly 12 pounds, with a roughly 8 foot wingspan. 

 

Their plumage is primarily dark brown and grey, with downy whitish grey feathers on the thighs, rump and at the base of the neck. They have a long, skinny, dark grey to blackish neck and head, with large dark eyes, and relatively large outer ear openings, on each side of the head. They have an imposing, squat, hooked bill, also dark grey, with two nostril slits at the upper base. Their legs, feet and toes are dark gray too, the toes are arranged in an anisodactyl formation, so three toes facing forward and one, the hallux, facing back, all with talons. Though unlike say an eagle or owl, vulture talons are relatively blunt, adapted for walking and stability, rather than grasping and killing.

 

The Slender-billed Vulture’s neck, head, legs, and feet are featherless. This is a kind of hygienic adaptation. They are deep-cavity scavengers; when they feed, they’ll often insert their heads deep into the cavities of rotting carcasses. Their bald neck and head means blood, rot, bacteria does not get stuck in feathers, helping protect the vulture from germs and potential disease.

 

Diet and Behavior

The Slender-billed Vulture is a carrion-eater, meaning they eat animals, generally mammals, which are already dead. They do not hunt and kill prey themselves, instead scavenging abandoned carcasses for the leftover, often rotting flesh, muscle, tissue, etc. They feed on the remains of larger mammals: cattle, buffalo, deer, and will visit human produced waste sites, seeking scraps in dumpsters and open landfills.

 

Vultures, including our Slender-billed Vulture, have highly acidic stomachs, so they can safely digest decaying meat contaminated with toxins, bacteria, and viruses that would be lethal to other animals. 

 

This may sound a little gross. That’s because our species, humans, cannot digest these nutrients without getting sick. In the millenia of human evolution, individuals who consumed rotting food were more likely to die and hence, not reproduce as frequently or successfully. So, while my explanation here is a kind of simplified version of natural selection, basically human individuals who recoil, who are repulsed by spoilt food, have historically been more likely to live longer and healthier to produce more and healthier offspring. So our instinctive reaction, that feeling of being grossed out, was ingrained over time, it is an evolutionary adaptation.

 

Of course, carrion-feeders, for whom this food is not a danger, do not have this selection pressure and so do not share that revulsion. Instead, decaying discards, abandoned or avoided by other species, are vital energy and nutrient resources to the vulture. This in turn serves a vital ecosystemic role, removing, cleaning disease-bearing carcasses from their habitat.

 

And the Slender-billed Vulture has its own adaptations for this diet. The stomach acid, their bald head and neck, and their slender bill, for which they are named, that allows them to dig deeper into carcasses, providing greater access to additional sustenance. They employ a “gorge and fast” strategy; because food access is unpredictable and can be sporadic they will consume as much as they can in one feeding. They hold excess food in a specialized internal storage organ called the crop, and then slowly break down the meal over several days, even up to a week: digesting, resting, and fasting.

 

The Slender-billed Vulture finds its food sources through high-altitude, visual searches. Like many birds, they have specialized feathers called filoplumes that are extremely touch sensitive, mechanoreceptors that sense air temperature, air pressure and wind speed, allowing the vulture to ride warm air updrafts, to soar, to maintain flight without expending significant energy flapping their wings.

 

From above in the sky, they use their well developed eyesight to scan their habitat for potential food. Vulture eyes are large in relation to their head size, and have a high density of rods and cones, allowing them to see fine details and small movement from thousands of feet in the air.

 

And, Slender-billed Vulture use social strategies to aid in foraging. They rely on a behavior called local enhancement. So a single vulture does not have the time or energy to scan its entire range, so instead they monitor the behavior of other vulture. If one vulture spies food and begins a rapid descent, other vulture in eyeshot will follow to that location, resulting in a kind of game-of-telephone across the sky, a long distance, visual communication of food source location, that in a kind of chain reaction can draw others from miles and miles away.

 

At a feeding site, though there is evidence of some displays of social dominance, peeking and vocalizing, the Slender-billed Vulture is generally gregarious. Many Slender-bills will feed on the same carcass simultaneously and peaceably share feed sites with other vulture species and even mammals like jackal or wild dog.

 

We have an audio recording, made by Phil Gregory in 2024 of a group of Slender-billed Vulture feeding on a carcass from a site in Cambodia. It is, um unexpectedly mellow, for a crew of raptor gorging on carrion. Let’s listen.

 

[SOUND RECORDING]

 

The grunts, croaks and guttural hisses we heard there, are the vulture’s primary vocalizations. They do not have a syrinx. That is the vocal organ that many birds use to produce their songs, whistles, calls and caws. Instead, vulture can only produce sounds by forcing air through their upper respiratory tract: these clacks, grunts, and croaks; a short-range communication mainly used at feeding and roosting sites.

 

Outside of the breeding season the Slender-billed Vulture will roost, will gather in small groups on the branches of tall trees to preen, that’s clean themselves, and sun. Sunning is a behavior in which the bird spreads their wings wide, with their back to the sun. The sun’s heat has a restorative effect on their feathers and the UV radiation is a kind of disinfectant, killing bacteria on places where the bird can’t reach, like their head and neck.

 

Reproduction

During the breeding season, that is October to March, the roosts will split into mating pairs. Slender-billed Vulture form longterm, multi-seasons pair bonds, and are solitary nesters. Mating pairs construct their nests at a distance from other pairs, unlike say birds who nest in group colonies. Nests are large structures constructed by both the male and female, of sticks and twigs, lined with leaves and grasses, usually 30-80 feet off the ground in the branches of tall sturdy trees. We have observed evidence of nest site fidelity. So once a pair has successfully built a nest, they may return to the same nest in later years, refurbishing it, annually. They’ll add new sticks, reline the base with new greenery, and because they add on every year, the nests can get really big over time, reaching widths of 3 feet in diameter and 2 feet deep.

 

Nest construction, or refurbishment, begins in October, and then the female lays a single egg in November or December. Both parents take shared responsibility, splitting-time incubating the egg, defending the nest, and scavenging food for themselves. The egg incubates for roughly 50 days, and the young is born altricial, requiring parental care. Both parents share responsibility for feeding the hatchling, bringing it semi-digested meat. The young fledges, that is, learns to fly and leave the nest, after about 3 months. But parental care, protection, education and socialization continues for several months more. A juvenile Slender-billed Vulture reaches reproduction maturity at about 5 years of age and they live for up to 30 years.

In The Dream

————

In the dream,

 

To soar,

 

Isn’t this always the dream?

 

To soar

To be wind-kissed, to be sun-soaked,

On a cloudless morning

A patchwork of greens and browns and blues

stitched out below

 

Buoyant on the currents, surfing updrafts,

Effortlessly drifting above it all.

We dream to be free.

 

Here on earth, in the dirt,

among the craven war-makers

The sky and everyone in it

Looks holy.

 

In the dream.

————

Habitat

The Slender-billed Vulture is native to South and Southeast Asia, specifically Nepal, India, Bangladesh, Myanmar, Laos, and Cambodia, with most of the remaining population found in the Terai region of India and Nepal. 

 

The Terai is a lowland belt across southern Nepal and northern India between the Himalayas and the Ganges River plains. This is a mix of open grasslands, subtropical deciduous forests, and wetlands, a mosaic of flat wide savannahs interspersed with scattered trees and major river systems.

 

The climate is humid, subtropical, significantly affected by the South Asian monsoon. Summer temps in the pre-monsoon months, April to June are intense with highs reaching above 110°F. Winter lows will drop into the mid-40s°F. Precipitation is also highly seasonal, with 80% of the year’s rain falling in June to September, monsoon season. Annual rainfall is high, averaging roughly 85 inches per year.

 

The Slender-billed Vulture shares its lowland home with:

Silk-cotton tree, White-rumped Vulture, Bengal Monitor Lizard, Haldu tree, Wild Boar, Munj Grass, Elephant Grass, Teak, Striped Hyena, Bengal Quince, Bengal Tiger, Spotted Deer, Asian Elephant, Sal tree, Golden Jackal, Indian Gooseberry, Indian Rock Python, Swamp Deer, Red-headed Vulture, Sloth Bear, Harro, Indian Vulture, Leopard, Greater One-horned Rhinoceros, Arjun Tree, and many many more.

 

Threats

In the late 20th century, the Slender-billed Vulture population suffered catastrophic decline, plummeting over 97% in about 15 years. The cause was the increased use of diclofenac, a non-steroidal anti-inflammatory drug  human farmers used to treat inflammation in their livestock. Initially we did not know that the drug is toxic and fatal to vultures. So when scavenging the carcass of cattle treated with diclofenac, they also ingest the drug which in vultures causes rapid kidney failure. A vulture will generally die within 48 hours of consumption.

 

And because the vulture are social foragers, and share food sources, the threat escalates: a vulture might lead an entire local population to a toxic carcass, resulting in death for all.

 

Fortunately, in 2006 India and Nepal banned the use of diclofenac for domesticated livestock.

 

That said this threat persists today, as other anti-inflammatory drugs that are equally toxic to vultures, are still in use and there is evidence of use of cheap diclofenac labeled for human-use still being given to cattle.

 

Additionally, Slender-billed Vulture population is threatened by intentional poisoning by poachers. The sight of circling vultures can alert park rangers to the location of an illegally killed elephant or rhinoceros, so poachers will poison carcasses to kill vulture, reducing potential congregations.

 

Conservation

Fortunately, the Nepalese and Indian governments and local and international non-governmental organizations are taking these threats to the vulture seriously. Banning diclofenac and advocating against the use of other anti-inflammatory drugs.

 

Nepal and India have created Vulture Safe Zones, protected areas, in which populations are monitored, outreach programs educate locals on the vital role of vulture in the ecosystem, and even establishing Vulture Restaurants. These Community-managed Supplementary Feeding Centers are fenced-in areas where elderly cattle are purchased from farmers, kept in “quarantine” to ensure any drugs have cleared their systems, and then humanely slaughtered, put out for the vulture to feed upon.

 

Since 2009, local captive breeding programs have successfully raised Slender-billed Vultures. And recent reintroductions have found that some released birds have already begun to breed successfully in the wild.

 

Nevertheless the Slender-billed Vulture has been considered critically endangered on the IUCN Red List since 2002 and their overall population is generally in decline.

 

Our most recent counts estimate that less than 870 Slender-billed Vulture remain in the wild.

Citations 27:51

Information for today’s show about the Slender-billed Vulture was compiled from:

 

Information for today’s show was compiled from

BirdLife International. 2021. Gyps tenuirostris. The IUCN Red List of Threatened Species 2021: e.T22729460A204781113. – https://dx.doi.org/10.2305/IUCN.UK.2021-3.RLTS.T22729460A204781113.en

 

BirdLife International (2021). Species factsheet: Slender-billed Vulture Gyps tenuirostris. –  https://datazone.birdlife.org/species/factsheet/slender-billed-vulture-gyps-tenuirostris 25/02/2026

 

del Hoyo, J., N. Collar, and J. S. Marks (2020). Slender-billed Vulture (Gyps tenuirostris), version 1.0. In Birds of the World (J. del Hoyo, A. Elliott, J. Sargatal, D. A. Christie, and E. de Juana, Editors). Cornell Lab of Ornithology, Ithaca, NY, USA.– https://doi.org/10.2173/bow.slbvul1.01

 

Hille, Sabine M., Fränzi Korner-Nievergelt, Maarten Bleeker, and Nigel J. Collar. “Foraging Behaviour at Carcasses in an Asian Vulture Assemblage: Towards a Good Restaurant Guide.” Bird Conservation International 26, no. 3 (2016): 263–72. – https://doi.org/10.1017/S0959270915000349

 

Jackson, A. L., Ruxton, G. D., & Houston, D. C. (2008). The effect of social facilitation on foraging success in vultures: a modelling study. Biology letters, 4(3), 311–313. – https://doi.org/10.1098/rsbl.2008.0038

 

Mundy, P. J., 2022. Measurements and shape of the Slender-billed Vulture Gyps tenuirostris. Indian BIRDS 18 (3): 82–85. – https://indianbirds.in/vol-18-no-3/

 

The Peregrine Fund. n.d. “Slender-billed Vulture.” Explore Raptors. – https://peregrinefund.org/explore-raptors-species/vultures/slender-billed-vulture

 

Prakash, Vibhu, Hemant Bajpai, Soumya S. Chakraborty, Manan Singh Mahadev, John W. Mallord, Nikita Prakash, Sachin P. Ranade, Rohan N. Shringarpure, Christopher G. R. Bowden, and Rhys E. Green. “Recent Trends in Populations of Critically Endangered Gyps Vultures in India.” Bird Conservation International 34 (2024): e1. – https://doi.org/10.1017/S0959270923000394

 

Ranade, Sachin P. 2025. “Time Activity Budget of White-Rumped Vulture and Slender-Billed Vulture During Breeding in Captivity.” bioRxiv. – https://doi.org/10.64898/2025.12.09.693217

Sound Recording by Phil Gregory. 2024. Xeno-Canto. XC899521 – xeno-canto.org/899521

 

Virani, M., P.C. Benson, M. Gilbert, and S. Thomsett. 2004. A survey of the reproductive activities at some Gyps vulture nests in Kanha, Bandhavgarh and Ranthambhore National Parks, India, in the 2002/2003 breeding season. Pages 263-268 in R.D. Chancellor and B.-U. Meyburg (Eds.) Raptors Worldwide. World Working Group on Birds of Prey and Owls, Berlin and MME/BirdLife Hungary, Budapest. – https://assets.peregrinefund.org/docs/pdf/research-library/2004/2004-Virani-vultures.pdf

 

Wikipedia – https://en.wikipedia.org/wiki/Slender-billed_vulture

 

Wildlife Institute of India (2018). National Studbook of Gyps Vultures (Gyps bengalensis, G. indicus and G. tenuirostris), Wildlife Institute of India, Dehradun and Central Zoo Authority, New Delhi.TR. No2018/38 Pages: 142. – https://cza.nic.in/uploads/documents/studbooks/hindi/Gyps%20Vultures%20(Gyps%20spp).pdf

 

For more information about Slender-billed Vulture conservation please see Saving Asia’s Vultures from Extinction at https://save-vultures.org.

Music 29:43

Pledge 37:03

I honor the lifeforce of the Slender-billed Vulture. I will commit its name to my record. I am grateful to have shared time on our planet with this being. I lament the ways in which I and my species have harmed and diminished this species. I grieve.

 

And so, in the name of the Slender-billed Vulture I pledge to reduce my consumption. And my carbon footprint. And curb my wastefulness. I pledge to acknowledge and attempt to address the costs of my actions and inactions. And I pledge to resist the harm of plant and animal kin and their habitat, by individuals, corporations, and governments.

 

I forever pledge my song to the witness and memory of all life, to a broad celebration of biodiversity, and to the total liberation of all beings.