Slender-billed vulture (Gyps tenuirostris)

Synonyms: Gyps indicus tenuirostris
GenusGyps (1)
SizeLength: 80 – 95 cm (2)

The slender-billed vulture is classified as Critically Endangered (CR) on the IUCN Red List (1). It is listed on Appendix II of CITES (3) and Appendix II of the Convention on Migratory Species (4).

This thin, scruffy vulture has a nearly naked black head and neck with a dark bill. The feathers on the rest of the body are brown, and the underparts streaked with pale brown. There are also patches of downy white feathers on the thighs that are clearly visible in flight. Juveniles are similar to adults but the head and neck have white down on top of the black skin (2).

Found in Bangladesh, India, Cambodia, Laos, Burma, Nepal, and Thailand (1), but now thought to be lost from Viet Nam and Malaysia (5).

The slender-billed vulture inhabits both open and partly wooded land, mainly in the lowlands. The slender-billed vulture is also found near human habitation and will scavenge from rubbish dumps and slaughterhouses (2).

An understudied bird, the slender-billed vulture has recently gained species status having been considered to be a subspecies of Gyps indicus prior to 2000. It builds compact nests in loose colonies of fewer than ten individuals at heights of seven to fifteen metres in large and leafy trees. The breeding season is between October and April, when pairs of vultures produce a single egg. Incubation duty is shared between both parents (5).

Feeding solely on carrion, the slender-billed vulture prefers the remains of cattle (5), but will also consume the carcases of wild deer and pigs killed by tigers (6), as well as meat discarded by humans (2). The slender-billed vulture tolerates the presence of other vulture and scavenger species while it eats, gorging itself, and then resting to digest the food (5).

The slender-billed vulture does not migrate, but when young or unpaired, can cover huge areas in flight (5).

Having suffered an extremely rapid decline in numbers due to a previously unknown cause, the slender-billed vulture is in danger of imminent extinction without immediate conservation action. By 2000, dead and dying Gyps vultures were being found so frequently in Nepal and India it was thought that they were suffering from an epidemic. The unnaturally high death toll was thought to be caused by a fatal virus, but testing has revealed that the vultures were suffering from kidney failure following the consumption of cattle that had previously been treated with the anti-inflammatory drug, diclofenac (2). In fact, the decline is a result of a lethal level of the drug in a small proportion of the ungulate carcasses available to vultures, but as vultures travel long distances to reach carrion, a considerable proportion of the population has been affected (7).

In the east of India, the almost complete loss of the slender-billed vulture occurred prior to the current drug disaster and is thought to relate to the reduction in large wild mammals, and the human consumption of livestock that dies naturally (2).

The full extent of the decline of slender-billed vultures, and other vulture species, is already felt by humans, as rotting carcasses remain untouched, posing a health hazard, as well as encouraging feral dog populations which carry rabies (8).

It is necessary to prevent exposure of vultures to livestock carcasses that have been contaminated with diclofenac, and to find an alternative replacement drug (7). Government commitment to the control of the use of the drug is crucial, but until it has been entirely removed from the environment, a collaboration of bird protection organisations plan to take all slender-billed vultures into captivity for the next 20 to 30 years to avoid further deaths, which would further reduce the chance of a successful recovery of this already rare species (8).

For further information on the slender-billed vulture see:

Authenticated by BirdLife International. and by Nick Lindsay, International Zoo Programmes, Zoological Society of London.

  1. IUCN Red List (March, 2008)
  2. BirdLife International (December, 2004)
  3. CITES (December, 2004)
  4. CMS (December, 2004)
  5. Peregrine Fund (December, 2004)
  6. BirdLife International. (2001) Threatened Birds of Asia: the BirdLife International Red Data Book. BirdLife International, Cambridge, UK.
  7. Green, R.E., Newton, I., Schultz, S., Cunningham, A.A., Gilbert, M., Pain, D.J. and Prakash, V. (2004) Diclofenac poisoning as a cause of vulture population declines across the Indian subcontinent. Journal of Applied Ecology, 41(5): 793 - 800.
  8. National Geographic News (December, 2004)