This article examines the plight of 10 endangered birds of prey that appear on the Red List of Threatened Species, compiled by the International Union for Conservation of Nature (IUCN). It looks at the conservation status of these birds, the threats they face, their surviving numbers and their future prospects. Some of the scavenger species may not be the most beautiful looking of birds, but their contribution to global biodiversity should not be underestimated. For other vulnerable bird species that are affected by rising temperatures, see: 10 Birds Threatened by Climate Change.
For details of other species at risk of extinction, see: List of Endangered Species. For specific profiles of iconic wildlife under threat, please see: 10 Endangered Animals. For risks connected to global warming, see: Effects of Climate Change on Animals.
Bald Eagles (like the one shown above) are not currently threatened although they have returned from the brink of extinction (in the USA), and climate-induced changes may still cause them serious problems. More frequent droughts, for example, degrade bodies of water that eagles depend on. The drying out of a river ecosystem affects its food resources like fish. The Audubon Society predicts that by 2080 three quarters of the bald eagles’ summer range will have vanished.
Their diet can vary enormously. They eat rats, mice, voles, gophers, rabbits, hares, ground squirrels and other mammals, as well as amphibians and reptiles. They also eat other birds. Some raptors feed almost exclusively on fish. In addition to live prey, they will also eat carrion if necessary. Some species, like vultures, feed almost exclusively on animal carcasses. Some large raptors will seize lambs or even small deer, while others eat mostly insects.
- What are Birds of Prey?
- Conservation and Threats
- IUCN Red List of Threatened Species
- 10 Endangered Birds of Prey
- 1. Californian Condor
- 2. Martial Eagle
- 3. Egyptian Vulture
- 4. White-backed African Vulture
- 5. Philippine Eagle
- 6. Forest Owlet
- 7. Madagascar Fish Eagle
- 8. Andean Condor
- 9. Indian Vulture
- 10. Red-Headed Vulture
- Endangered Birds of Prey: Conclusion
What are Birds of Prey?
In ornithology, birds of prey – also known as raptors – are defined as any bird that has a keen sense of vision, sharp talons and a strong hooked beak capable of tearing flesh. However, ornithologists argue over the usefulness of this broad definition, since the appearance, diet and habitat of raptors can vary widely.
Birds of prey are the apex predators of the avian world. The main species of raptor include: eagles, hawks, falcons, kestrels, ospreys, vultures, condors, buzzards, kites and owls.
They have excellent eyesight for spotting potential victims, sharp talons for grasping and killing them and powerful often heavy curved beaks for gouging flesh. Owls, who hunt at night, possess an acute sense of hearing.
Birds of prey are found in almost every type of biome on Planet Earth, from the Arctic tundra or taiga to the Sahara Desert. They are able to circle for long periods, before silently swooping down at high speed to snatch their prey. But they can also be seen soaring on rising thermals, sometimes for several hours, in search of carrion. Condors, for example, will often travel 250 km (160 mi) a day in search of food.
Conservation and Threats
Conserving the health of these birds by safeguarding them where possible against human threats, is a vital priority. Why? Because, as apex predators, they help to maintain the health of the biomes and ecosystems in which they operate – just as sharks help coral reefs to remain healthy and lions help wildebeest herds to stay disease-free. So, by protecting raptors we also protect lots of other species in the biosphere, thus maintaining the planet’s wonderful biological diversity.
In addition, birds of prey like vultures serve as invaluable detritivores, recycling precious nutrients from the remains of animals back into the food web, for the benefit of all. Like decomposers, they act as the planet’s recycling and clean-up crew.
Unfortunately, raptor conservation isn’t easy. First, their large range means that regional rather than local conservation strategies are needed. Second, their opportunistic style of hunting can lead them into trouble. They can end up being shot on sight, killed by poisoned bait, left out for other predators like foxes, coyotes or wolves. In addition, any pesticides that enter the food chain lower down, or lead-shot in dead but unretrieved game birds, are inevitably going to end up in a raptor’s diet.
The loss of habitat – that is, disappearance of trees, decline in water supply, reduction in prey – is the single biggest threat to raptor populations. Climate change can be a cause of habitat reduction, but the main culprit is human development in the form of livestock farming, deforestation, mining and road-building. Death caused by electrocution from or collision with power lines and pylons is another major cause of raptor death, notably in Europe and southern Africa.
The main bird conservation organizations who work to mitigate the loss of biodiversity within the avian kingdom, include: BirdLife International 1, The National Audubon Society 2 and The Royal Society for the Protection of Birds. 3
IUCN Red List of Threatened Species
The IUCN Red List is the world’s most authoritative list of endangered species. 4 According to BirdLife International, the body that compiles data on endangered bird species for the IUCN Red List, 5 states that around 1,375 bird species (about one in eight of the total) are threatened with extinction – that is, they are either vulnerable, endangered or critically endangered. 6
10 Endangered Birds of Prey
1. Californian Condor
After becoming extinct in the wild in 1987, numbers of these condors have since risen to over 400, thanks to the US Department of the Interior, who has reintroduced them to Zion and Grand Canyon National Parks. However, even now there are only 44 mature individuals in the wild. The main threats to their recovery is lead poisoning (from eating carcasses containing lead shot), poaching and habitat destruction – in fact even small losses of habitat can have a major impact on their survivability. 7
Californian Condors live in coniferous forests, rocky shrublands or lightly forested grasslands, typically where oaks are the dominant trees. Nesting sites are usually located in cliffs or large trees. Like all condors, these birds have a huge range, travelling up to 250 km in search of food.
To safeguard the current small population, Californian Condors are monitored and treated for lead poisoning, without which their numbers would most likely plummet once more. The condors ingest the lead after scavenging the carcasses of animals that were killed by lead shot or bullets. Over time, levels of lead build up in their system until they die. Their life cycle habits of not breeding until they are six years old, and only having one chick every other year, leaves them vulnerable as a species. 8
Sanctuaries dedicated to Californian Condors include: the Sespe Condor Sanctuary in the Los Padres National Forest, and the Sisquoc Condor Sanctuary in the San Rafael Wilderness. In addition, there are separate release sites in Arizona and Mexico. The Californian Condor is classified as critically endangered by the IUCN.
2. Martial Eagle
The Martial Eagle, native to sub-Saharan Africa, is one of the largest and most powerful species of eagle. It’s a member of the booted eagle subfamily (Aquillinae) and is identifiable by the feathering on its legs. It has a large wingspan measuring around 2.6m (8.5 feet). It lives in wooded belts of otherwise open savanna, preferring desolate or protected areas. It can spot prey from up to 6 km (3.7 mi) away and feeds on mammals (like hares, monkeys, pangolins, korhaans, dik-dik antelopes, or any species of hyrax or mongoose), birds (like guineafowl and bustards) and reptiles. Occasionally it will seize more aggressive animals, such as poisonous snakes, monitor lizards, jackals and wild cats. 9
It also takes livestock and regionally valuable game, triggering serious reprisals from local farmers and game wardens. Populations have fallen in many areas. For example, due to persecution by farmers in the Transvaal Province of South Africa, the Martial Eagle population fell by two-thirds from about 1,500 in 1950s, to fewer than 500 by the 1990s. This, despite the fact that domestic livestock like goats and sheep accounts for only about 8 percent of its diet. The Martial Eagle is classified as vulnerable to extinction by the IUCN. 10
3. Egyptian Vulture
The Egyptian Vulture, also known as the white scavenger vulture, has white feathering with a bright yellow bill and face. Ornithologists believe it to be intelligent due to its use of tools. For example, it drops pebbles to crack open large eggs, and uses twigs to roll up wool to line its nest. Its diet is highly varied and includes small mammals, birds, reptiles, tortoises, carrion, organic waste and even faeces. However, it feeds primarily on carcasses of dead animals. It is nature’s waste disposal service and plays a vital role in preventing the spread of diseases.
This species of vulture can be found anywhere from Portugal, through North Africa, to India. They roost communally in cliffs, large trees or even buildings, typically close to a waste site or other foraging area. 11 Its eastern populations (those that breed in the Balkans, Turkey, Central Asia, India and the Middle East) migrate thousands of kilometers to spend the winter in Sahel Africa and Saudi Arabia.
It is now listed as globally endangered due to a major drop in numbers. In Europe, for instance, its population has fallen by more than half over the last 50 years, and in the Balkans, over 80 percent have been lost over the past 30 years. In 2007, the total population was estimated at between 21,000 and 67,000 birds. The major threats to the Egyptian vulture include deterioration and loss of habitat along their migration routes; food shortages due to the commercial development of former feeding grounds; and accidental poisoning caused by the eating of poisoned bait intended for predators like foxes. Global warming exacerbates the loss of habitat through the drying out of water sources, and other effects of warming.
4. White-backed African Vulture
The white-backed African vulture is a medium-sized vulture, with a 6-7 ft wingspan and a body weight of about 4-7 kilograms (9-16 lbs). Its whitish back contrasts with the rest of its otherwise dark plumage. It nests in tall trees (such as mopane, acacia or any of several thorn trees), often in colonies, on the grasslands of western, eastern and southern Africa.
They often scavenge in flocks, feeding mostly on the remains of animals which it spots as it soars over the African landscape. Although no vulture is ever likely to win a beauty contest, they play a critical role in local ecosystems, cleaning up the environment by devouring rotting carcasses.
White-backed vultures used to be one of the most widespread and common vulture species on the African continent. In recent years, however, numbers have begun to rapidly decline – disappearing altogether from parts of their range – making it one of the most endangered birds of prey in Africa.
A major cause of the drop in numbers is the loss of habitat. The main cause is human development encroaching into the wild. For example, farmers often deliberately target their nesting trees to drive them out of the area. Habitats are also being degraded by various forms of human land use change and land management. 12
Elephants are another culprit, since they strip and destroy the trees the vultures live in, which is why vultures tend not to nest in areas with lots of elephants.
Humans also affect vultures in other ways. They hunt them for bush-meat and for body parts for the traditional medicine (muthi) trade. They also use a toxic pesticide called Furadan which has caused numerous vulture deaths in East Africa, as have other chemicals such as diclofenac 13 and a group of substances known as HPAs (polycyclic aromatic hydrocarbons).
In addition, Earth’s climate crisis affects rainfall, wind speeds and temperatures, all of which can adversely affect younger birds.
In 2012, the species was listed as Endangered. In 2015, its status was changed to Critically Endangered.
5. Philippine Eagle
The Philippine Eagle, also known as the Monkey-eating Eagle, is one of the world’s largest, most powerful birds of prey and a marvellous example of our threatened biodiversity. It is distinguished by its brown-feathered, manelike crest, a creamy-brown neck, bluish-grey hooked beak and heavy yellow legs and large talons. It averages around 3 feet or more in length, weighs between 4 and 8 kg (roughly 9-18 lb) and has a 2m (6.5 feet) wingspan. Only the Harpy eagle (Harpia harpyja) and Steller’s Sea Eagle (Haliaeetus pelagicus) are heavier.
These birds are monogamous and mate for life, sharing a long breeding cycle that lasts for two years.
The species is unique to the rainforests of the Philippines, but its numbers are rapidly declining and it has hovered on the brink of extinction for decades. As an attempt at conservation, it has now been declared the Philippine National Bird, in order to boost awareness of its plight. The killing of an eagle is now punishable under Philippine law by up to 12 years in prison. Even so, it remains a critically endangered species, largely due to the effects of deforestation on its habitat, caused by commercial logging, expansion of plantations, mining operations, and pesticide contamination of the food chain. For more, see: Deforestation in Southeast Asia.
Rainforests are vital habitats for all kinds of animals and plants. The largest example is the Amazon Rainforest in South America, 60 percent of which is in Brazil. Unfortunately, deforestation in the Amazon Rainforest – caused mostly by commercial development and slash and burn farming – is having a serious effect on biodiversity within the animal and bird kingdom throughout the biome.
To cap it all, the Philippines are among the world’s ten countries that are most vulnerable to the risks of climate change, notably extreme weather events such as tropical storms. 16 The islands of the Philippines are located in the middle of the typhoon belt, with around eight or nine making landfall, each year. The worst recent example being Typhoon Haiyan (Nov 2013).
Despite efforts in the 60s and 70s to protect the eagle, such as the 1969 Monkey-eating Eagle Conservation Program, its population in the wild was estimated in 2015 at no more than 600 eagles, and it remains one of the most endangered birds of prey in southeast Asia. 17 The only safety factor against gradual extinction is the Philippine Eagle Foundation in Davao City, which has managed to breed Philippine eagles in captivity for over a decade.
6. Forest Owlet
Unique to the forests of central India 18, this species of owl was originally classified alongside three others as Athene blewitti, but has since been reclassified as the sole member of Heteroglaux blewitti. Unlike its many of its relatives, the Forest Owlet is diurnal, hunting rodents, lizards, birds and small mammals only in daylight hours. They are noted for their unusually large claws, which they use to trap prey sometimes twice their size.
The forest owlet is small – roughly (23 cm/9 in) in height – and stocky. It has a relatively large head and beak, and only a few spots on its crown and back. Its upperparts are dark grey-brown, while its primary feathers are dark, while its wings and tail are banded with white trailing edges. It nests in Tectona grandis, Lagerstroemia parvifolia, Boswellia serrata, Soymida febrifuga and Lannea grandis trees, at a height of 5.0m (16.5 feet) and upwards.
The forest owlet scans the forest for prey from favored perches, before swooping. More than three quarters of its diet comes from lizards and rodents, with the rest coming from birds, frogs and other amphibians. 19
Previously believed to be extinct, the species was rediscovered in November 1997 by a team of American ornithologists in the foothills of the Satpura Hills, in the state of Maharashtra, some 83 years after the last sighting. Its stronghold appears to be in the protected Melghat Tiger Reserve in Maharashtra, where over 100 individuals have been recorded. At the same time as surveys continue to find new individuals, agriculture, illegal logging, deforestation, forest fires, and construction of irrigation dams, is causing a continuing loss of habitat with inevitable consequences for the owlet population.
In 2018, the forest owlet was classified as endangered on IUCN’s Red List, with an extremely small and fragmented population estimated at 250-1,000 mature individuals.
7. Madagascar Fish Eagle
The Madagascan Fish Eagle (Haliaeetus vociferoides), also known as the Madagascar Sea-eagle, is one of the most endangered birds of prey. It is unique to the northwest coastal strip of the Island between Morondava and Antisiranana, notably the Analova region. It measures around 2 feet in length and weighs 5-6 pounds. It has a light brown head, dark brown body and white tail, and its beak and talons are also dark brown. As the name indicates, it feeds almost exclusively on fish.
These eagles have very low reproductive rates. 20 The female usually lays one or two eggs but only one offspring survives, as the stronger chick usually kills the weaker.
The population of Madagascan Fish Eagles has been steadily declining from its very small base. IUCN estimates the total number at no more than 40 breeding pairs – hence its classification as critically endangered. According to the eagle expert Rebecca L. Grambo, it is one of the rarest birds on earth.
As with all birds of prey, threats to the Madagascan Fish Eagle come mainly from humans. Its fish diet, for example, brings it into direct conflict with Malagasy fishermen, leading to death and injuries from shooting as well as entanglement in fishing nets. The species is also threatened by loss of habitat, caused by forest clearance, soil erosion and the expansion of rice-paddies.
Deforestation, soil erosion and the development of wetland areas for rice-paddies is causing the on-going loss of nesting and foraging habitat. There is an ongoing conservation programme with the aim to increase the known breeding population to at least 250 pairs. 21
Biodiversity among plants is of critical importance to all species of wildlife. Plants perform a vital role in the carbon cycle, by absorbing carbon dioxide from the air, through the process of photosynthesis. In addition they play an important part in the water cycle through the mechanism of transpiration, by which they release water vapor into the air. Plants and trees within the Amazon Basin, for example, actually create their own weather system.
Soil also plays a critical role, as it supplies nutrients needed by plants and trees. For more, see: Why is Soil So Important to the Planet?
8. Andean Condor
The Andean Condor is one of the world’s largest flying birds with a wingspan up to 3.3m (10 ft 10 in), exceeded only by the 3.5m (maximum wingspan of two seabirds – the Wandering Albatross (Diomedea exulans) and the Southern Royal Albatross (Diomedea epomophora) – and the 11.8 ft maximum wingspan of the two water birds – the Great White Pelican (Pelecanus onocrotalus) and the Dalmatian Pelican (Pelecanus crispus). Its wingspan combined with a weight of up to 15 kgs (33 lbs), makes the Andean Condor the largest bird of prey in the world.
It is found in the mountains of the Andes and in alpine regions and open grasslands along the adjacent Pacific coasts of western South America. It lives primarily in mountainous regions because it needs strong wind currents to help keep its massive body in flight. It
Considered a vulture, the Andean Condor is a large black bird with fluffy white feathers around the base of its neck and large white patches on its wings. Like all vultures, its dull red head and neck are almost completely devoid of feathers. Unlike many birds of prey, the male condor is bigger than the female.
Noted for its long life span – up to 70 years in some cases – the condor breeds at around five or six years of age and lays its eggs on inaccessible rock ledges up to 5,000m (16,000 ft) above sea level. It produces only one or two eggs, and it lays them not in nests but among boulders or in holes or caves, making it harder for other predators to target them.
Like all vultures, the condor is mainly a scavenger, feeding on large carcasses of deer or cattle, although it also preys on small rodents as well as young animals and eggs of larger species.
The Andean condor is the National Animal of Colombia and a national symbol of Argentina, Bolivia, Chile, Ecuador, and Peru, but its population remains vulnerable. It was put on the Red List of Threatened Species in 1970 and despite the success of several captive breeding programs, it is still considered near threatened by the IUCN and the Peruvian Conservation Organization. This means it is believed to be in danger of extinction across all or a significant part of its range. 22
The main threats to the Andean Condor – which apply mostly to its presence in Venezuela and Colombia – include: loss of habitat in which to forage, due largely to land use change; and lead or chemical poisoning from animals shot by hunters, or baited by farmers worried about raptor attacks on livestock.
Conservation efforts, instituted in several South American countries, have focused on educational campaigns to educate farmers about the relatively harmless nature of the condor, and captive breeding programs. Condors released into the wild are monitored by satellite for scientific and conservation purposes.
9. Indian Vulture
The Indian vulture – similar to the Slender-billed Vulture (Gyps tenuirostris) – is a medium-sized bird with a bald head and neck, pale underparts and underwing, grey-brown feathers and a long, hooked bill. It has an average wing span of 2 to 2.5m (6.5 to 8 ft) and body weight of 6 kg (14 lb). It nests in colonies on hilly crags and cliffs, and occasionally in trees, in central and southern India.
During the 1990s, researchers noted an unusual decline in vulture populations in India. Then in 2002 scientists identified accidental poisoning by the veterinary drug diclofenac as the cause of the decline. 23 Diclofenac is an anti-inflammatory drug given to working animals to reduce joint pain and extend their working life. The drug is ingested by vultures when scavenging the flesh of dead cattle. A subsequent study of carcasses indicated that about 10 percent were contaminated: ten times the number needed to cause a 90 percent fall in vulture numbers.
As a result of this poisoning, the Indian vulture – along with the White-rumped Vulture (Gyps bengalensis) and the Slender-billed Vulture – has suffered a 97 percent drop in numbers across Bangladesh, Pakistan and India.
The decline in the Indian vulture – a natural animal-carcass disposal system – has had a major impact on the conservation of the environment. By getting rid of all animal remains, vultures have always played a hugely important role in the prevention of disease, reduction of pollution and the suppression of other undesirable scavengers. This is critical in India, where only 4 percent of its 500 million cattle are consumed (due to the Hindu religion), leaving many of the others to die and decompose in the fields, villages and towns.
With the collapse in vulture populations, feral dogs and rats have multiplied, leading to numerous health problems. The trouble is, a vulture’s metabolism erases all pathogens, but dogs and rats simply become carriers of disease. What’s more, the now 18-million strong population of wild dogs is beginning to attract the attention of leopards, with added risks for humans.
10. Red-Headed Vulture
The Red-headed Vulture (Sarcogyps calvus) is an Old World vulture found mainly on the Indian subcontinent, with small separate populations in parts of Southeast Asia, such as Cambodia and Laos. They are found in a variety of habitats – grassland, river valleys, deciduous forest – up to elevations of 3,000m above sea-level. 24 It is one of the few species of vulture that does not live in colonies. Instead it lives alone or as part of a breeding pair. 25
It is a medium-sized vulture, typically averaging around 3 feet in length, 5 kg (11 lb) in weight, with a wingspan of about 2.5m (8 ft). It has a bare head, usually deep-red/orange in colour (paler in young birds), on top of a black body with a pale grey band at the base of the wing feathers.
Like most vultures Red-headed Vultures eat mostly carrion, feeding on carcasses of large ungulates, as well as birds, fish and turtles.
Red-headed vultures used to range throughout the Indian subcontinent, and eastwards to south-central and south-eastern Asia – an area extending from India to Singapore. Today, however, its range is limited primarily to northern India. This is partly because of a sudden collapse in its population – 90 percent over 10 years in India alone – which has occurred since the 1990s. The culprit is diclofenac, a veterinary drug administered to draught animals to ease inflammation and thus prolong their usefulness.
As recently as 2003 the species was ranked in the Least Concern category on the IUCN Red List, before being classified as Near Threatened (2004) and Critically Endangered (2007). Today its population is estimated at no more than 10,000 mature individuals, down from a population of several hundred thousand a few years ago.
Endangered Birds of Prey: Conclusion
Birds of prey are a vital and critical part of the ecological process.
First, they occupy the top of many food chains. As a result, ornithologists see them as a sort of ecological barometer – a way of gauging what’s happening within the ecosystem at large.
If their numbers are high, it generally means that food is abundant and the remainder of the food chain is healthy. Conversely if numbers fall, it signals a problem. For example, in the 1950s and 1960s, the sudden decline in numbers of peregrines and other raptors alerted scientists to the damaging effects of organochlorine pesticides.
Second, birds of prey (along with other predators) help to balance the size of animal populations that are lower down in the food chain, such as field mice and rats, squirrels, rabbits, and other rodents, as well as amphibians, reptiles and even fish.
This is the main ecological benefit of all animal predators. Take the African Crocodile, for example, who is often filmed attacking helpless wildebeest and other herbivores as they swim across the Mara River in the Maasai Mara/Serengeti game reserves. If crocodiles (and lions) didn’t regulate the numbers of grass-eating animals like wildebeest, zebras and the like, then soon there would be no grass left for any of the animals to eat, and the ecosystem would collapse.
Third, birds of prey (like vultures) who feed on dead animals and other waste, may not be the most popular of species, but without them the world would be much less healthy. The decline of the Indian vulture and its consequences for humans and other animals, is a perfect example of how important these creatures are.
In a nutshell, biological diversity (variety of species) is critical to maintaining the ecological balance. If human development, or rising temperatures caused by man-made climate change, continue unchecked, the resulting loss of biodiversity could lead to very serious consequences for us all.
- BirdLife International
- The National Audubon Society
- The Royal Society for the Protection of Birds.
- The IUCN Red List.
- Bird species for the IUCN Red List.
- BirdLife Factsheet.
- “Lead poisoning and the deceptive recovery of the critically endangered California condor.” Myra E. Finkelstein, et al; PNAS 109 (28) 11449-11454; July 10, 2012.
- “FAQs About Californian Condors.”
- See also: “Ranging behaviour and habitat preferences of the Martial Eagle: Implications for the conservation of a declining apex predator.” Rowen van Eeden et al; PLOS One. March 17, 2017.
- “Investigating the decline of the Martial Eagle (Polemaetus bellicosus) in South Africa.”
- M. J. McGrady, D. L. Karelus, H. A. Rayaleh, M. Sarrouf Willson, B.-U. Meyburg, M. K. Oli & K. Bildstein (2018) “Home ranges and movements of Egyptian Vultures Neophron percnopterus in relation to rubbish dumps in Oman and the Horn of Africa.” Bird Study, 65:4, 544-556
- “Nesting habitat preference of the African White-backed Vulture Gyps africanus and the effects of anthropogenic disturbance.” Bamford, A. J., Monadjem, A., Hardy, I. C. September 16, 2008.
- Vultures Conservation Society.
- “Another Continental Vulture Crisis: Africa’s Vultures Collapsing toward Extinction.” Darcy Ogada et al.; Conservation Letters. June 18, 2015.
- “Major declines in the abundance of vultures and other scavenging raptors in and around the Masai Mara ecosystem, Kenya.” Munir Z Virani. Biological Conservation 144(2):746-752. February 2011.
- “Global vulnerability to sea level rises worse than previously understood.” Climate Central.
- The Philippine Eagle Foundation.
- “Interspecific interactions of the critically endangered Forest Owlet (Athene blewitti)“. Reuven, Y. et al; (2010). Acta Ethologica. 13 (1): 63–67.
- “Diets of Sympatric Forest Owlets, Spotted Owlets, and Jungle Owlets in East Kalibhit Forests, Madhya Pradesh, India“. Mehta, P.; Kulkarni, J.; Talmale, S. & Chandarana, R. (2018). Journal of Raptor Research. 52 (3): 338–348.
- “Madagascar Fish Eagle productivity in the Tsimembo-Manambolomaty Protected Area and surrounding habitat of western Madagascar.” Gilbert Razafimanjato, et al; (2018) Ostrich, 89:2, 117-122.
- See also, “Factsheet: Madagascar Fish-eagle Haliaeetus vociferoides.”
- “Assessing population size and structure for Andean Condor Vultur gryphus in Bolivia using a photographic ‘capture-recapture’ method.” Diego Mendez, Stuart Marsden, Huw Lloyd. Ibis, Volume 161, Issue 4. Pages 867-877. October 1, 2018.
- “Identification of a Novel Mycoplasma Species from an Oriental White-Backed Vulture (Gyps bengalensis)“. Oaks, J. L. et al; (2004). Journal of Clinical Microbiology. 42 (12): 5909–5912.
- Ferguson-Lees, James; David A. Christie (2001-09-17). Raptors of the world. Houghton Mifflin Harcourt. pp. 443–444. ISBN 978-0-618-12762-7
- “Red-headed Vulture (Sarcogyps calvus)”