The kings of the birds, the great and majestic eagles, belong to the family Accipitridae, along with the buzzards, kites, harriers, and the true accipiters, the hawks and goshawks. The Old World vultures also belong to this large and diverse family.
There are 234 species of hawk that range from small sparrowhawks to the largest Martial Eagle. They all have a hooked bill for hunting live prey, which ranges from worms and beetles to fish, bats, and birds.
Together with the Falconidae, these families of birds are often referred to as the birds of prey or raptors. They are generally large birds with sharp talons and powerful, grasping feet with which they are able to kill quite large animals and sharp, hooked bills that are ideal for tearing flesh.
Most species are expert gliders capable of soaring effortlessly for hours with barely a movement of the wings. With the larger species flapping flight is generally to get airborne, but the true accipiters are strong and agile fliers capable of following and catching a small bird as it darts among the trees of a forest.
Hunting methods vary with species. The larger eagles tend to cruise in the hope of surprising prey or coming across carrion, while kites are great scavengers, and buzzards hunt from a low perch. All have large eyes set well forward on the head, giving good binocular vision.
In some species, the sexes have a distinct plumage, and in most, the female is considerably larger than the male. In the accipiters, this size difference can even lead to the male and female taking different-sized prey.
The fact that these birds are slow to mature, and pass through a succession of immature plumages, is confusing enough to the would-be raptor watcher. Even when fully adult, however, they are by no means easy to identify.
To pick out a bird in flight as belonging to a group is not that difficult. Eagles have large, broad wings, medium-length tails, and prominent heads. Buzzards also have broad wings, but their tails are short and spread, and their head is very small.
Hawks have long tails, broad, rounded wings, and are generally smaller. Harriers have long, narrow wings and tails and a flapping, lazy flight low over the ground, but when they soar, they can be confused with kites. Fortunately, the latter has a characteristic notch or deep fork in the tail.
The largest and most regal of all the birds of prey are the eagles of the genus Aquila, but even these vary from the magnificent Golden Eagle A. chrysaetos, which hunts over mountainous areas and is quite capable of killing small sheep, to hangers-on at rubbish tips like the Lesser Spotted Eagle A. pomarina.
The Golden Eagle was once found across Eurasia and North America, but persecution waged over centuries has driven it into the hills. Golden Eagles are highly territorial birds and have the habit of nesting at only one or two traditional sites generation after generation.
They have therefore been easy prey to gamekeepers and hunters in the past. Mostly they nest on crags, although in some parts of the range, they will use trees. Golden Eagles lay two eggs but rear only one youngster.
Even when food is plentiful, the elder sibling will consistently kill the younger. This habit is quite common among birds of prey. The Lesser Spotted Eagle does the same, although experiments in eastern Europe have shown that Common Buzzards Buteo buteo make excellent foster parents, and can help a declining eagle population.
The huge Verreaux’s or Black Eagle A. terreauxi is not uncommon in southern and eastern Africa. Its staple diet is Rock Hyrax, but it will take large birds up to the size of guineafowl.
In flight, its all-black plumage is broken only by patches of white on the wings, rump, and back, but this bold pattern, plus the look of its wings where they join the body, gives it a distinctive flight silhouette.
The Tawny Eagle A. rapax is the most abundant of the large eagles. It is found throughout the Old World and is successful partly because of its adaptability.
It takes carrion quite freely, will steal off other predators, and has been seen flying high up around Mount Everest. It is quite capable of hunting for itself and will kill rodents on the ground and strike birds in the air.
While it is not unusual to see single birds perched on roadside trees and telegraph wires, Tawny Eagles also gather in flocks at carrion.
In Australia, the Wedge-tailed Eagle A. audax has been persecuted because of its alleged depredation of sheep. While they do take lambs occasionally, they are quite incapable of killing sheep. They will feed on dead lambs and sheep afterbirth.
They are fond of carrion, and poisoning in the past seriously reduced the numbers of Wedge-tailed Eagles in many parts of Australia. However, they are still common in non-farming areas. Rabbits are a staple food, but wallabies are the natural food.
While the eastern race of the Imperial Eagle A. heliaca seems to be holding its own, the Iberian race, the Spanish Imperial Eagle A.h. adalberti, is classed as vulnerable by the IUCN Red List. The population numbers are increasing, but it will take many years before their numbers are stable. They are large, handsome birds that feed on carrion and small mammals.
Similar to some of the Aquila eagles and almost as large, the genus Haliaeetus comprises a worldwide group of eagles who like fish. Many species are called fish eagles, although the most famous is the Bald Eagle H. leucocephalus, national symbol of the United States.
Formerly common throughout North America, this eagle has been reduced to a few widely scattered pockets where it survives only under rigorous protection. The largest numbers are found in Alaska.
When large numbers of eagles can be seen feeding on salmon, and large numbers also gather along Alaskan rivers to feed on the dead and dying shoals of Sockeye Salmon, which have just spawned.
African Fish Eagle
While some fish eagles are expert fishermen, many are scavengers that like dead or dying fish. They will gather at carrion or pursue other birds like Ospreys until they disgorge, but their fishing efforts are quite facile.
However, the African Fish Eagle H. vocifer is, as its scientific name implies, a very vocal species with a shrill, far-carrying cry and is a particularly good fisher. The eagle will swoop down in a gentle curve from its lookout post to snatch a fish from near the surface.
In Kenya’s Rift Valley, Lake Naivasha is divided into Fish Eagle territories, and a bird stands every couple of hundred yards along the shore, protecting its fishing patch. Immature birds either trespass or feed from the center of the lake.
Steller’s Sea Eagle
Largest of all is the Steller’s Sea Eagle which feeds on fish, large birds, and mammals up to the size of an Arctic fox.
Its brown plumage is broken only by the white tail and under-tail coverts and a white patch at the bend of the wing. It has a huge, orange bill which is easy to spot and is confined to the most northern part of Japan and adjacent parts of the Siberian coast.
The Harpy Eagle Harpia harpyja is a huge, powerful bird with a white facial disc and two erectile, black tufts to its crown. It feeds in tropical jungles on monkeys, lemurs, and other tree-dwelling mammals, which it grabs as it glides among the trees below the canopy.
The Philippine Eagle Pithecophaga jefferyi, or monkey-eating eagle, is a closely related, though less powerful species in imminent danger of extinction due to habitat loss and deforestation. These species bear some similarities to the various hawk eagles of Africa.
They are the largest eagles in length and wing surface area, although not as heavy as the Harpy eagle and Steller’s Sea Eagle. In 2105, there were only about 600 Philippine Eagles alive.
The Osprey is the only bird of prey that is a pure fisher. It is also known as the fish hawk, river hawk, and sea hawk. It can be found in many habitats and catches fish by diving feet first into the water. It is particularly fond of trout and pike but will take whatever is available.
They are a large raptor, brown on the underparts and greyish on the head and underparts. The osprey has several adaptations that put it in its own genus.
They have closable nostrils to keep water out when diving, reversible outer toes, oily plumage to stop them from getting waterlogged, and talons with barbs to hold fish.
Buzzards are similar to eagles but built on a smaller scale. They are scavengers, but most feed on small mammals as well. The typical buzzards of the genus Buteo, known as hawks in North America, are widespread except in Australia and Malaysia.
They are excellent at soaring and can be seen perching on posts to hunt for small prey. They are mainly shades of browns and are sometimes diffcult to identify in the field, although some species, like the Augur Buzzard B. rufofuscus, are well marked.
This African bird occurs in two distinct forms, a dark and a light one. Both have dark, slate grey backs and a distinguishing rusty red tail. They are common birds seen on telegraph posts in East Africa and often hover like some other Buteos.
The Red-tailed Hawk B. jamaicensis also has a rusty tail, as do some of the eastern populations of the Common Buzzard.
The Rough-legged Buzzard B. lagopus has a polar distribution, and frequently hovers like a Kestrel in its search for small mammals. Like other Arctic predators, it is dependent on the population of Lemmings and flies southwards with them over a four or five-year cycle. Rough-legged Buzzards make lengthy sea crossings, which is unusual for a raptor.
Being soaring birds, most migratory raptors keep clear of the sea where thermals are not available to give them the lift that they require. Thus European raptors avoid crossing the Mediterranean by flying the narrow straits at each end at the Bosporus and Gibraltar.
In North America, raptors follow the Appalachian mountain chain where lift is freely available on the updraughts of air that mountains create. Hawk Mountain in Pennsylvania regularly attracts large numbers of bird watchers who gather at migration time to see these dramatic movements.
Harriers are another cosmopolitan group. They scan the ground, flying with bouts of flapping interspersed with glides on long, V-shaped wings. They are graceful birds and feed mainly on dead or injured birds.
In several species, the male is a pale grey and the female a dull, mottled brown. Several species are associated with marshes, and the Hen Harrier Circus cyaneus is known as the Marsh Hawk in North America, different to the Marsh Harrier C. aeruginosus of Eurasia. Several species are migratory, making long journeys across the Sahara to winter in East and West Africa.
Although they bear a superficial resemblance to harriers, kites are more closely related to the fish eagles than the harrier subfamily Circinae. The Brahminy Kite Haliastur indus is a reddish bird with the white head and shoulders of the African Fish Eagle, but bearing a stronger resemblance in habits to some of the other fish eagles.
Kites are essentially scavengers that spend most of their time in the air searching for food. They are expert fliers and can hang stationary on the wind for minutes at a time.
Their position is maintained by moving the tail and only minimally using their wings. This ability to hang in the air gave rise to the name kite.
The various black kites are the commonest scavengers in cities throughout the world, although it seems that it was the Red Kite Miltus milvus that was the scavenger of the streets of medieval London. Red Kites are solitary, woodland birds with deeply forked, translucent, red tails.
Nevertheless, from Cairo to Kathmandu and Nairobi, black kites hang in the air and drop to the streets for scraps. As these cities were cleaned up, kites have slowly started to disappear.
The New World has kites of its own, the most remarkable of which, the Snail Kite Rostrhamus sociabilis, feeds entirely on a diet of Pomacea snails. It was formerly quite common in the southern parts of the United States but has almost disappeared, except in Florida.
It is a long-legged bird that hovers low over marshy pools where the snails live. When one is caught, it is taken in the feet to a post or other perch, where the adapted bill extracts the animal from its shell with a twist. The Hook-billed Kite Chondrohierax uncinatus performs a similar job on land snails.
The birds of the subfamily Elaninae are also called kites, but they are quite distinct from other species. Typical and widespread is the Black-winged Kite Elanus caeruleus of Africa, Asia, and Australia.
It is a grey, white and black bird that can be seen hovering while searching for prey or perching on telegraph poles. In the western Palaearctic, it is confined to a few pairs in Spain, Portugal, and northern Morocco.
Over the rest of its range, it is an obvious and easy to see bird. It is replaced by the very similar White-tailed Kite E. leucurus in America.
The related Swallow-tailed Kite Chelictinia riocourii of Africa is one of the most graceful birds in the world. With grey and white plumage and a forked tail, it catches insects as it flies.
It should not be confused with the American Swallow-tailed Kite Elanoides forficatus, which feeds entirely in the air catching insects with its feet.
The Bat-hawk Machaerhamphus alcinus is crepuscular and emerges from its daytime hideaway only when its prey, small to medium-sized bats, are flying.
It is a silent flier and comes out of the dark to grab a bat in flight. It is nowhere common over its range in East Africa and Asia and is solitary and difficult to see. It also takes swallows as well as bats to vary its diet.
The honey buzzards of the subfamily Perninae are a loosely related group of birds that are difficult to fit in elsewhere in systematic order. The Honey Buzzard Pernis apivorus is a buzzard-like bird with broad, barred wings but with a larger tail and small head set on a pigeon-like neck.
It is a migrant to Europe and northern Asia, where it feeds on the grubs of wasps and has a special covering of armor-like feathers to protect it from these insects’ stings. It has a remarkable display flight in which the bird raises its wings and flies, moving around like a butterfly.