The slender-billed vulture (Gyps tenuirostris) is a critically endangered Old World vulture species native to Southeast Asia and Sub-Himalayan areas.
This species used to be known as the Indian vulture, but due to the differences in regions and appearances, they were subsequently given their own name based on – you guessed it – their slender bills.
Due to the conservation status of the slender-billed vulture, it is imperative that we take the time to learn about these magnificent birds. Here is the ultimate guide to the slender-billed vulture!
Appearance
The slender-billed vulture looks almost exactly how you would expect a vulture to look – intimidating, large, and somewhat prehistoric. They weigh 4-7 Kg and have a wingspan of approximately 6-8 ft.
These vultures are similar in size to the Indian vulture, with heights of between 31-37” tall, making them a medium-sized vulture. Their black neck is long and slim with no feathers, and as the name suggests, these vultures possess a dark and slender, slightly hooked bill.
These vultures are predominantly gray in color, with the occasional shade of sandy brown or grayish white. Their thighs are the most white part of their bodies, and their dark narrow heads display an exposed ear opening.
The legs and feet, like their necks, are dark gray. When they open their wings, the slender-billed vulture looks something like a large bat, with its bony elbows and haunting physical features.
Male vs Female
As the slender-billed vulture was previously considered a subspecies of the Indian vulture until it gained its own classified species name, there is little research about the differences between male and female slender-billed vultures.
If we look at vultures in general, who are sexually dimorphic, then we can assume that slender-billed vultures are just the same.
In short, as it can be so difficult to find the sexual organs of a vulture without plucking at their feathers, a DNA test would be required to determine the sex of the bird. This means that it is hard to distinguish the differences between a male and female slender-billed vulture.
Are They Aggressive?
As there has been limited research on the behavior of the slender-billed vulture, we can only make an educated guess as to what their behavior and aggression levels are like.
No human is wise enough to go near a slender-billed vulture given the behaviors of most vulture species. If, for example, we look at black vultures who are notoriously aggressive, we can assume that slender-billed vultures aren’t the friendliest of creatures.
When it comes to animals, slender-billed vultures aren’t likely to be kind, either. These birds usually feed off carcasses, but nothing will stop them from attacking a live animal – whether injured or not.
What Adaptations Do They Have?
Due to lack of research, it’s hard to say what adaptations these Old World vultures have. This is mostly because the slender-billed vulture was considered a subspecies of the Indian vulture, which also isn’t said to have developed many adaptations.
We can assume that the reason no adaptations have been discovered is that slender-billed vultures, like most vulture species, have perfected their survival and hunting techniques over the centuries.
Therefore, they have found no need to create physical adaptations in order to survive.
Breeding / Reproduction Behavior
Unfortunately, little is known about the breeding and reproduction behavior of slender-billed vultures. This is partly due to the lack of research about the species, and partly because it’s very difficult to distinguish between male and female vultures.
What we do know is that the breeding season is generally between October and March, and both parents share the responsibilities of parenthood somewhat equally. While the male is nesting, the female will scavenge for food, and vice versa.
Firstly, the adults both make a large, bulky nest 7-15 meters from the ground. This is usually in the canopies of trees, on cliff edges, or buildings.
As for the courting and mating ritual, aerial displays have been discovered above the nests, which we can only assume is the vulture’s language of love. Calls and sounds are also made, which is the standard courting ritual amongst most birds.
Once the mating ritual has been successful, the female vulture will lay a singular white egg with pale red blotches. The incubation period usually lasts 50 days, after which the chick is fed from its nest for several weeks until the fledging period.
Their Calls / Sounds
Slender-billed vultures don’t make any particular distinguishable sounds or calls, except for the occasional hissing and cackling.
These sounds are usually made to communicate with other vultures when prey (or in the rare occasion, a predator) is nearby, or during the courting and mating rituals. They will also make grunting noises when they are scavenging or tearing apart a carcass.
What Do They Eat? (Diet)
It’s no secret that vultures are notorious scavengers. Slender-billed vultures are no exception – they will feed off the carcasses of dead animals, injured live animals, any scraps lingering around, and even anything they can find from dumpsters.
Where Do They Live? (Habitat)
The slender-billed vulture is native to Southeast Asia and sub-Himalayan regions, including north and central Bangladesh, Burma, Cambodia, and southern Nepal.
This is why they are classified as an Old World vulture species, which are species found in Europe, Asia, and Africa. These vultures tend to stay away from human settlements, so they are most commonly found in dry open country or wooded areas.
What Are Their Nesting Habits?
Slender-billed vultures will make their nests with a partner (or even several other vultures) out of sticks and twigs. These nests are dense and slightly dipped in the center, and are usually located in the canopies of trees.
They will also sometimes be on cliff edges or on abandoned buildings.
How Long Do They Live? (Lifespan)
The estimated lifespan of the slender-billed vulture is 20 years.
What Predators Do They Have?
Slender-billed vultures have possibly one of the most unexpected predators in the world – the veterinary drug, diclofenac.
In the mid-2000s, the slender-billed vulture species dramatically declined after studies revealed that they were feeding off the carcasses of livestock that had been treated with diclofenac (an anti-inflammatory), which causes fatal kidney failure in vultures.
Studies revealed that these declining figures were also a result of the drug ketoprofen, which was present in the carcasses of ungulates (large mammals with hooves).
Poisoning of animals in general has been the biggest threat to slender-billed vultures who then eat the animals.
Deforestation and habitat destruction have also led to a significant decrease in food sources, especially in Cambodia where the figures of ungulates are decreasing.
As a result of this, it is safe to say that while no animal poses a threat to the slender-billed vulture, humans are their main predators.
What Are Their Feathers Like?
Slender-billed vultures have no feathers on their neck, head, or feet. Their main plumage is on their body, where the feathers are different shades of gray and sandy brown. Their thighs are made up of a white, fluffy down.
What Does Their Poop Look Like?
Slender-billed vulture poop looks pretty similar to most feces from vultures – it can range from yellow to black to brown, and often comes out in a liquid-like consistency due to the uric acid that kills bacteria in the food they eat.
Do They Migrate?
Slender-billed vultures are not migratory birds. They tend to stay in the same location, only moving to find food. When they do fly to find food, they can have a flight speed of up to 90 mph, which is all down to their impressively large wingspan of 6-8 ft.
Conservation Status
Unfortunately, according to the IUCN Red List, slender-billed vultures have a conservation status of Critically Endangered.
Due to a significant decline in population figures in the mid-2000s as a result of the veterinary drug diclofenac found in livestock, it is estimated that less than 1000 slender-billed vultures remain in the wild.
However, this figure was estimated back in 2009, so numbers could be far less.
To try and combat these figures, captive-breeding facilities in India have worked to keep the vulture species safe in their facilities until the poisonous diclofenac is no longer present in the wild.
Even though the retail sale of diclofenac is illegal in India, it can still be illegally acquired.
There is also currently a breeding colony of approximately 50-100 vultures in Cambodia’s Steung Treng province. The reason this is so successful is likely because diclofenac isn’t available in Cambodia.
Fun Facts
The slender-billed vulture is an Old World vulture species, which is a group of birds belonging to the Accipitridae family who are native to Europe, Asia, and Africa. Other Old World birds include eagles, hawks, buzzards, and kites.
The slender-billed vulture used to be known as a subspecies of the Indian vulture, known as the “long-billed vulture”, but when scientists realized both species live in different ranges and are very clearly distinguishable animals, the “long-billed vulture” was given its own species name – the slender-billed vulture.
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