The Slender-billed Vulture (Gyps tenuirostris) is an Old World Vulture from the Gyps genus. A long and slender bill gave the vulture its name. With wingspans mearuring between 234-260 cm this is one of the larger vulture species.
The Slender-billed Vulture is a native to the Indian subcontinent and distributed in lower Himalaya, Pakistan, North India, Nepal, Bhutan, Burma, Thailand, Malaysian peninsular and south Laos.
Once a common vulture in South Asia
Until the early 1990s this species was one of the most common vultures in the countryside and urban areas and metropolitan cities. They used to gather in their hundreds on squares and near slautherhouses, and were by no means afraid of mankind. Despite their dark appearance, society accepted them as vital for the disposal and processing of carcases, carrion and human corpses. Unfortunately, in our days they have come close to extinction.
Distribution and Populations status of the Sleneder-billed Vulture
The Slender-billed Vulture is, in together with the White-rumped Vulture and the Long-billed Vulture, one the most endangered vulture species in the whole of South Asia. In India, the Slender-billed Vulture suffered a near total collapse in population numbers. From the beginning, the reason for this dramatic development was unclear for quite some time. Only after long and thorough resarch the reason was found. But in the meantime the Slender-billed Vulture suffered a decline in number by 97% and came close to extinction.
The reason for this catastrophic decline was found in a painkiller (diclofenac), which was used quite successfully in veterinary and human medicine. However, no-one could ever have forseen the effects this agent could have on vulture populations.
Reason found
The Slender-billed Vulture has had a quite a status as processor of animal and human corpses in India and the adjacent countries. Therefore, this vulture fell victim the a painkiller. As a matter of fact, vultures can take up and digest any sort of corpse poisioning without suffering any harm. Though, a simple painkiller knocked the vultures out in the thousands. The Indian government took immediate action and banned this agent for use in veterinary medicine. Alas, nearly too late for the vultures, because with a population down to 3 pc of its former size, extinction is nearly immient. Vultures are the last link in the food chain which makes them most vulnerable.
Reproduction Rate and Survival
Vultures usually have a re-production rate <1 because they mainly lay only one egg. Under such circumstances any species can only very slowly recover at all. That means that all losses above the re-production rate can hardly be compensated. Moreover, only 50% of all fledged juveniles of the Gyps species only reach the end of their first year. Only 8 % become sexually mature. Taking all that into account only breeding and release into the wild in national reserves can help these vultures.
Population Status of the Slender-billed Vulture
The total population of the Slender-billed Vulture is estimated at 1,500-3,700 individuals in the whole of South Asia. Breeding and support propgrammes in national reserves made a survival of the species possible. In national parks it is possible to release young vultures into safe areas where they are fed with special and clean food. A start has been made but there is still a long way to go.
Characteristics of the Slender-billed Vulture
Taxonomy
Order: Accipitriformes
Family: Accipitridae
Genus: Gyps
Species: Slender-billed Vulture
Scientific Name: Gyps tenuirostris
Names and Synonyms of the Slender-billed Vulture
German: Dünnschnabelgeier or Schmalschnabelgeier
French: Vautour à long bec
Dutch: Dunsnavelgier
Italian: Grifone beccosottile
Spanish: Buitre picofino
Portuguese: Grifo-de-bico-estreito
Finish: Gangesinkorppikotka
Danish: Smalnäbbad gam
Swedish: Smalnäbbad gam
Polish: Sęp bengalski
Nepali: सानो खैरो गिद्ध
Bengali: সরুঠুঁটি শকুন
Malaysian: Burung Hereng Paruh Panjang
Thai: อีแร้งสีน้ำตาล, อีแร้งสีน้ำตาลหัวดำ, อีแร้งสีน้ำตาลหิมาลัยgam
Chinese: 细嘴兀鹫
Chinese (traditional): 細嘴兀鷲
Viet Nam: Chim Kền kền Ấn Độ
Russian: Тонкоклювый сип
Distribution – Movements – Habitat
Distribution: Indomalayan. Distribution area covers Pakistan, Nepal, Bhutan, north and east of Burmaa, Cambodia, south Laos, Malaysia, Thailand, the northwest of India towards the Assam.
Movements: Slender-billed Vultures are sedentary. Food shortages may lead to evasive movements in order to survive. Immature Slender-billed Vultures are nomadic.
Habitat: wetlands and wooded areas. also near settlements, open countryside. Settles also in lower mountain range in altitudes of up to 1,000 m; also sub-himalayan ranges.
Behaviour of the Slender-billed Vulture
Slender-billed Vultures are very good at gliding. Processes carcases, always away on search flights to find new food. Glides up to altitudes of 1,500 m. At feeding places Slender-billed Vultures mostly appear in small groups and socialises with Lappet-faced Vultures and White-rumped Vulture, though they give way to the latter ones. The pecking order at carcases is as follows: Lappet-faced Vulture – White-rumped Vulture – Slender-billed Vulture. Regular guest at landfills and slaughterhouses.
Field Characteristics of the Slender-billed Vulture
With regard to body size and wingspan, the Slender-billed Vulture is very similar to the Long-billed Vulture. Though, in contrast to the latter one, the Slender-billed Vulture has a slim body. A very short tail is barely covers the legs during flight. As usual for Gyps species, the wings are broad and long. The first primaries are shorter than the inner primaries. Dark head and neck. Most obvious to the observer are: small head, large eyes; longer bill and leggs compared to other vultures species. Bulging secondaries give the long, broad wings a pinched-in look. Dark primaries, secondaries and tail, compared to pale coverts.
Eyes: dark
Bill: long and dark with pale culmen
Cere: dark
Legs: dark
Measurements
Size: 93-100 cm
Tail: 24-26 cm
Weight: 4,000-7,000 g
Wingspan: 234-250 cm
Wing: 590-607 mm
Voice
Slender-billed Vultures utter buzzing and grunting sounds most often when feeding. However, these sounds are also used as intraspecific method of communication at any other time.
Breeding
Sexually mature: probably in the 5th year, simulatenously with moulting into the adult plumage.
Mating: Mating starts prior to courtship and subsequent breeding as early as October.
Clutches per breeding season1 clutch
Breeding: as early as October, mostly between December and January, Burma from October
Nest: Large platform from sticks and branches, decorated and lined with twigs, fresh and fresh green. Nest stands on large trees, usual in heights between 7-15 m, also on ledges.
Clutch: 1 egg
Eggs: egg with white shell and reddish staints and speckles
Egg Measurements and Weights
Length x Width: 92.5×69.3 mm
Weight: ≈ ??? g
Recurrent Clutches: not porbable.
Incubation: 50 days; ♂ and ♀ share the task of incubation
Fledging: Chicken is fed by both parents. There are no firm data with regard to fledging, though a period of 80-90 days can be assumed.
Dependency: As is customary wih Gyps vultures, the young Slender-billed Vulture will be dependent on ist parents for feeding and education at least for several weeks. Though, there are no firm data existing.
Miscellaneous
Food: The Slender-billed Vulture fully depends on the abundance of carrion. Carcases of cattle, all sorts of fallen game, human corpses, also dead cattle after outbreaks of cattles diseases. In India the Slender-billed Vulture once played a central role as the processer and disposer of human corpses, and carcases, which was accepted and expected by natives. These vultures also used to populate landfills and slaughterhouses.
Longevity: unknown.
Mortatlity: unknown.
Threats to the Slender-billed Vulture
Threats: Main threats are targeted poisoning, persecution in Laos, loss of food in Cambodia, deforestation in Nepal. By early 2000 the Slender-billed Vulture also fell victim to the painkiller Diclofenac which was use in veterinary medicine. By consuming dead cattle that previously had been treated with Diclofenac, the vultures suffered and died from instant multiple organ failure. Within a short period the population crashed by devastating 97%.
References and Links
Brown, Leslie, Die Greifvögel, Ihre Biologie und Ökologie, Paul Parey Verlag Hamburg und Berlin, 1979
Ferguson-Lees, James and Christie, David A., Raptors of the World, Houghton Mifflin Company Boston New York, 2001
Ferguson-Lees, James, Christie, David, Raptors of the World, A Field Guide, Christopher Helm London, 2005, reprinted 2019
Fischer, Wolfgang, Die Geier, Die Neue Brehm-Bücherei, A. Ziemsen Verlag Lutherstadt Wittenberg, 1963
Grzimek, Bernhard et al (HG), Grzimeks Tierleben, Band VII, Vögel 1, Kindler Verlag AG Zürich, 1968
Weick, Friedhelm, Die Greifvögel der Welt, Verlag Paul Parey Hamburg und Berlin, 1980
Links
EAZA Ex situ conservation programmes: https://www.eaza.net/conservation/programmes/
Action Plan for Vulture Conservation in India: pdf file
Asian Species Action Partnership: Slender-billed Vulture
Article: Now, another veterinary painkiller is accelerating extinction of vultures in India
Image Credits
Featured Image of the Slender-billed Vulture – source: neil bowman/agency iStock
Post image of the Slender-billed Vulture – source: neil bowman/agency iStock
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