The Slender-billed Vultures (Gyps tenuirostris) is a recently recognised species of Old World vulture. Slender-billed Vulture, a species that was once seen flying across the skies of South Asia and is now often overlooked, plays an important role in nature’s cleanup crew. It prevents diseases from spreading by eating animal carcasses.
The Slender-billed Vulture’s story is a valuable lesson for bird lovers all over the world, including in Australia. It teaches us about conservation and the impact human medicine has on wildlife. This bird is not native to Australia, but its dramatic decline in population and ongoing recovery efforts have made it a symbol of the importance of protecting species that scavenge for food.
Slender-billed Vultures are fascinating to birdwatchers, nature enthusiasts and those who want to know more about endangered species. The Slender-billed Vulture is a fascinating bird. Its unique beak shape, its special diet, and its strong gliding ability are all things to admire.
For some time, it was lumped with its relative, the Indian Vulture, under the name of “Long-billed Vulture”.
However, these two species have parapatric or allopatric ranges and can be immediately told apart by trained observers, even at considerable distances.
Description
Slender-billed vultures are a striking Old World vulture, and their long, narrow bills inspired the name. The sharp, elongated bill is well adapted to reach deep into carcasses for feeding, which allows the bird to access tissue that other scavengers may miss.
The Slender-billed vulture is a large bird with an impressive wingspan ranging between 234 and 260 centimetres. The plumage of the Slender-billed Vulture is mainly dark grey or black with a bald neck and head. This helps them to stay clean when they are feeding on carcasses. They are graceful gliders with sharp eyes and a graceful flight style.
The vultures in this group are all part of the Gyps family, which is a large carrion-eating bird found throughout Africa and Asia. The Slender-billed Vulture is similar to the Long-billed Vulture in appearance, but it tends to live in eastern South Asia. It also has a slightly different beak and head shape.
Behaviour
The Slender-billed vultures are expert gliders who use thermals and rising air currents to soar for long distances. The Slender-billed Vultures spend most of the day searching for carrion in large areas. They can locate carcasses from miles away because of their sharp eyesight and excellent flying ability.
These vultures tend to feed in small groups. There is a hierarchy of vultures at carcasses. The Lappet-faced vulture tends to dominate the feeding sites. White-rumped vultures are next, and Slender-billed vultures usually feed after they have eaten their share. They are persistent and manage to feed well despite this pecking order.
It is also known that they mix with other vultures in feeding areas and landfills. They have relatively peaceful interactions, unless there is a lack of food. They are not vocal but communicate with low grunting and buzzing sounds. This is especially true when they are feeding or establishing social space.
Diet / Feeding
The Slender-billed Vulture is a carrion feeder, feeding almost exclusively on carcasses such as cattle, buffalo and deer. They also ate human remains in the past during traditional sky burials. This highlights their role as a natural waste disposal.
The birds do not hunt live prey, but instead use their keen vision to find dead animals in the air. They feed with other scavengers after spotting the carcass. Their beaks are used to tear flesh and consume the nutrient-rich remains.
They often visit open graveyards, waste dumps and slaughterhouses. These sites are dangerous due to the contamination of treated livestock. To ensure their survival, they must guarantee food safety. According to Audubon Society, this species is well documented.
Songs / Calls
The Slender-billed Vulture is not known for its melodic songs, but instead produces low buzzing sounds, hissing noises, and grunting noises. They are most often heard when birds gather to feed, particularly when there are multiple birds. According to BirdLife International, this species is well documented.
These sounds are used to communicate, whether it is to establish dominance, show discomfort or warn of danger. During nesting, similar calls are made. Their vocalisations, while often silent when perched or flying, provide insight into social behaviour.
Breeding
The Slender-billed vulture begins its breeding season in early October. However, the majority of activity occurs between December and January. Nesting can begin earlier in some areas, such as Myanmar. These birds nest in tall trees that are usually between 7-15 metres high. However, in some places, they can also use rocky ledges.
Their nests consist of large flat platforms constructed from branches and sticks. Interesting, they decorate or line their nests with green leaves or twigs. This may be to add insulation or signal nest activity. Nests are reused each year and added to, increasing in size over time.
Each breeding pair will lay one egg per season. The egg is white, with speckles and reddish stains. The chick remains dependent on both parents for several months following hatching. Diclofenac-free zones are critical to their recovery because successful breeding depends on food safety.
Habitat
The Slender-billed vulture is usually found in areas with open land and light forest, particularly in the lowlands and lower foothills. The Slender-billed Vultures tend to avoid dense forest areas and prefer habitats that allow them to easily see carcasses. These birds usually live at elevations of up to 1,500 metres.
Vultures are commonly seen in human settlements. This is especially true around rural and urban areas with livestock farming. Vultures are often seen in places like open fields, slaughterhouses and rubbish dumps where dead animals may be dumped. These places provide vultures with a plentiful, but grim, source of food.
The habitat of these vultures has been fragmented by urbanisation and changes to livestock management. Conservation efforts are now focused on identifying zones where vultures may breed and feed without being exposed to harmful substances.
Distribution / Range
This species has suffered a marked decline in its numbers in recent years. Wild populations remain from northern and eastern India through southern Nepal and Bangladesh, with a small population in Burma.
The only breeding colony in Southeast Asia is in the Steung Treng province of Cambodia. This colony is thought to number about 50–100 birds.
The survival of the vultures in Cambodia may have been partly because diclofenac, which is poisonous to vultures, is not available there.
Conservation
The Slender-billed Vultures is a protected species listed on the Appendix II list of CITES, because its numbers have declined rapidly. Its decline is largely due to the use of the non-steroidal anti-inflammatory drug (NSAID) diclofenac in working farm animals, especially in India.
Diclofenac is poisonous to vultures, causing kidney failure, and is being replaced by meloxicam (another NSAID), which is not toxic to Vultures.
Captive-breeding programs in India are aiming to conserve the species, and it is hoped that vultures can be released back in the wild when the environment is free of diclofenac.
