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Birds of prey, also known as raptors, are divided into two main groups, the diurnal (day flying) birds of prey and the nocturnal (night flying) birds of prey, better known as the owls.
Raptors, like all other living organisms, were originally classified by anatomical, structural (their physical shape or build), or ecological (their environmental) characteristics (i.e. raptors were birds with clawed feet, sharply curved beaks, and that ate meat). The original classification system has seen many changes in recent years, especially with advances in genetic research, and as such, the classification system is subject to frequent and on-going updates as new research studies emerge.
Of course it should be remembered that classifying animals is an entirely human activity and thus nature often does not see clearly defined distinctions the same way humans do; however understanding where things fit in leads to better understanding of them and their needs.
Within both the diurnal and nocturnal groups, species are further classified into smaller groups. We have provided a general outline of these groups below. Further and more detailed information and updates on individual species can be found on specialist websites such as the Global Raptor Information Network (GRIN), the BirdLife International Data Zone and the International Union for the Conservation of Nature (IUCN) Red List of threatened Species. There are hundreds of other websites on raptors, but not all of them rely on peer-reviewed scientific data so their information should be treated cautiously.
Kingdom Animalia > Phylum Chordata > Class Aves
The New World Vultures
The New World vultures are all the vultures from North and South America, including the two species of condors. This group contains the smallest of all the vultures (American Black Vulture) and the largest (Andean Condor), which incidentally is the bird with the largest wing area of all birds. The Turkey Vulture, sometimes inaccurately also know as the Turkey Buzzard (although it is most definitely not a buzzard), is possibly the commonest raptor in the Americas. The King Vulture is one of the most colourful of all the raptors and is found in Central and South America. There are seven species of New World vulture and one of these, the California Condor, is the rarest vulture in the world. Its population declined dramatically in the 20th Century, mostly due to lead poisoning and habitat change, and in 1987 only 22 individuals existed, all of them in captivity. Thanks to a breeding programme run initially by the San Diego Zoo and the Los Angeles Zoo, and later joined by The Peregrine Fund, there are now over 300 California Condors, half of which have been through the release programme and are now starting to breed in the wild.
Like all vultures, the New World vultures specialize in eating carrion (dead animals). Unusually, the Turkey Vulture has a highly developed sense of smell, so by flying slowly over the forest canopy, this bird can find carcasses hidden by trees and the undergrowth only an hour after the animal has died. Other species of vulture have learned to follow the Turkey Vultures as a way to find food in thick cover. All the vultures are superb flyers and the smaller ones can soar for many hours on the tiniest of air currents; the larger birds need more robust air currents and uplift to be able to soar, which is why their habitats include mountainous areas.
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The Falcons and Caracaras
The Falconidae (scientific name for this large group) comprises four different groups – the caracaras, the forest falcons the pygmy falcons and the true falcons.
The caracaras do not look much like the falcons, but there are similarities and the eggs they lay are exactly the same mottled brown colour. They all inhabit Central or South America. The Common Caracara (or Crested Caracara) is the best documented, and this species is also found in the southern United States. Several of the other caracara species are still little understood, probably because they live in forests, which makes their study quite difficult. Most of the caracaras have long strong legs as they spend a great deal of time on the ground. They are very intelligent birds and although they hunt small mammals and occasionally birds, they are opportunist feeders and will eat carrion and even rotten fruit.
The forest falcons live in the forests of Central and South America. The first study on the breeding biology of this group was only undertaken in 1992, so we still know very little about these birds. They all look somewhat ‘hawk like,’ they often nest in cavities (trees, caves and sometimes buildings) and they lay whitish eggs rather than the typical brown mottled eggs of the true falcons and caracaras. They feed on a wide variety of forest fauna – insects, birds, snakes, reptiles and small mammals, although the diet of several species is still poorly known.
The smallest of all the diurnal raptors are the falconets. One species comes from South America – the Spot-winged Falconet, one species from Africa – the African Pygmy Falcon, and six species from South East Asia. They all nest in holes or old bird nests and they lay white eggs. Most are quite vocal and perform a visual display with head bobbing and tail flipping. They feed mainly on large insects, small birds, reptiles and the occasional mammal. The smallest weighs under 50 grams and the young hatch at just under 5 grams.
The true falcons group includes the well-known Peregrine, the Eurasian Kestrel and the Gyrfalcon. There are 13 species of kestrels worldwide; the largest is the Greater Kestrel (also known as the White-eyed Kestrel) from Africa, and the smallest is the American Kestrel found in both North and South America. Most of these little birds live in a wide variety of habitats including towns, farmland, woodland edges and can also inhabit more open areas. Most live on insects, reptiles and small mammals and most use a hovering technique to hunt for prey.
Other true falcons include the Merlin, Hobby, and New Zealand Falcon. These birds do not have the ability to hover like the kestrels and most live in the more open areas of habitat. Many of the large falcons live on open plains, mountains, deserts, savanna and similar terrain. Being larger, they hunt larger prey including birds and mammals, but also insects in some areas. They have long toes and their feet are not as powerful as the hawks, but the beak is very powerful. If their prey is not killed instantly by the speed of the falcon’s stoop, the true falcons use a special tooth on the beak (called the tomial tooth) to break the victim’s neck. Nearly all the falcons have long pointed wings and fairly short tails and most have dark brown eyes. None of the falcons build their own nest, but many either dig a ‘scrape’ on the ground or on a cliff ledge or even on a ledge on the side of a high-rise building. Some of the kestrel species will nest in trees cavities, and Merlins can nest either in heather on the ground or in an old-disused bird’s nest in a tree.
The Hawks and Eagles
The term ‘hawk’ is a little misleading as it is often used to describe a number of different things ranging from a group of raptors to an individual species. Here it is a general term used to describe a group of birds of prey. This group covers hawks, eagles, kites, Old World vultures, buzzards and many others. This is a huge group with (at the time of writing) 237 species recognised under the scientific name Accipitridae.
This group includes the bazas, very odd birds of prey that are thought to be closely related to the kites. They tend to be forest living birds and are found in Africa, South East Asia and Australia. They have fairly weak feet and beaks and they all eat insects, frogs and other small prey items.
The kites are a well-known group with a wide distribution in Europe, North and South America, Africa, Asia and Australasia. The Red Kite from Europe is the largest of the kite family, weighing over 1,000 grams and the smallest is the tiny Pearl Kite from South America, weighing only 80 – 100 grams. Most of the kites feed on insects, reptiles or small mammals, but a large number also scavenge. They all have relatively short legs and weak feet. The largest prey item the Red Kite takes is baby rabbits, but like many of the kites it often eats carrion, which leads to mistaken assumptions that it kills larger prey than it actually can. Kites have small feet and talons in comparison to the size of the bird – a sure sign of weak feet and thus small prey. The commonest of all the kites is the Black Kite. Also very common is the Brahminy Kite – this is a fishing kite and it looks like a tiny African Fish Eagle with large areas of white feathering. Like the fish eagles, this kite snatch-lifts small fish from the surface of rivers, lakes and estuaries.
Normally placed in this group are the Honey Buzzards. These are very kite like, but lack the forked tail that marks many of the kites. The Honey Buzzards are perhaps the most specialised, raiding wasp and bee nests to feed on the grubs. Thousands of Honey Buzzards migrate south from Europe and Asia in the autumn.
The fish eagles (also known as sea eagles) include some very well known species, such as the Bald Eagle from North America, the White-tailed Sea Eagle from Eurasia and the African Fish Eagle. The largest of the fish eagles is the Steller’s Sea Eagle. This stunning bird is one of the four ‘huge’ eagles in the world; it has enormous feet and a massive yellow beak, and lives on the far north eastern Chinese and Russian coastline and in parts of Japan. It is interesting to note that many of the fish eagles have either white tails, or other large areas of white plumage. All the fish eagles catch fish by snatch-lifting them from the surface of the water, but most of them will eat other prey as well. In fact most of them are very generalist feeders, eating almost anything they can find, including carrion. The exception is the Madagascar Fish Eagle, a highly specialised fish eater that rarely eats anything else. The fish eagles are also dramatic flyers, particularly the White-bellied Sea-Eagle from South East Asia and Australasia, which often engages in dramatic cart-wheeling flight during territorial and mating displays.
The Old World vultures are also in this group. Unlike the New World vultures, their feet are more eagle-like and you can’t see right through their nostrils (or ‘nares’) as you can with the New World vultures. The smallest is the Egyptian Vulture, which is found in Africa, Europe and Asia. It is called the Egyptian Vulture because it is depicted in the hieroglyphics on the Egyptian tombs. It is also one of the few birds of prey known to use tools, as it breaks open large eggs by throwing stones at them. The largest of the Old World vultures is probably the Eurasian Black Vulture, also known as the Cinereous Vulture (and not to be confused with the New World Black Vulture). The vultures in Africa are estimated to eat 40% of all the dead animals on the Serengeti Plain, competing with large carnivores such as lions, cheetahs and hyenas. If it were not for the vultures around the world there would be much more disease, as the vultures clear away all the dead and diseased animals. Their digestive systems are specially designed to cope with the high levels of bacteria found in decaying carcasses. In recent years, some vulture populations in Asia have undergone a catastrophic decline, due to the effects of a veterinary drug called Diclofenac. Many conservation groups are now working hard to try to prevent these vultures from the very real threat of extinction.
The Bearded Vulture is generally placed here although it is not actually related to most of the other vultures. It is a huge bird and feeds almost exclusively on bones. It picks up large bones that it can’t swallow and flies up and drops them onto the mountain side to break them into smaller pieces. It is the only diurnal raptor that does not have a crop (a small storage pouch in the throat).
The snake eagles, as their name suggests, eat snakes as well as other prey items, especially reptiles. The Bateleur is a bit of an exception as it will take small mammals and eat carrion as well. Most snake eagles have large heads and eyes and very tough scales on their feet to protect them from snake bites. Almost all have yellow eyes and none are found in the New World. Most have a short crest of feathers at the back of their head. When catching snakes they puff up their feathers and the snakes will strike at the nearest object, which is the outer part of the feathers, and is therefore less dangerous to the bird.
There are 13 species of harriers found around the world. All have a slight facial disc of feathers round the eyes, similar to the owls although not quite as obvious. This facial disc helps them to use their hearing to locate prey items in long grass or other vegetation. All have long broad wings, but a tiny lightweight body in comparison to their visual size, giving them what is called a ‘light wing loading’. This provides them with the ability to hunt by flying low and slow, again a little like some of the owls, looking and listening for mice and voles and small birds. They tend to live in marshland, coastal, arable farm land and moorland areas. They have long legs and weak feet. In many harrier species the males are a different colour from the females. The Hen Harrier has the dubious honour of being the most persecuted raptor in the British Isles. It is relentlessly and illegally killed by gamekeepers on commercial grouse moors, who blame the harrier’s taste for red grouse as a threat to their commercial livelihoods.
There is an assortment of other raptor species which are hard to place within the classification system. Some are more closely related to the former sub family – the harriers, and some are nearer to the accipiters or ‘true hawks.’ The Gymnogene (also known as the African Harrier Hawk), is a large, lightweight bird similar to the harrier, but it has a double-jointed ankle, which allows it to bend its foot the ‘wrong’ way. This adaptation enables it to take baby birds or small mammals from inside hollow trees or from holes in cliffs by putting its leg inside and hooking out the prey. Also in this group are the chanting goshawks from Africa, which really do live up to their name and have a glorious song, and the Gabar Goshawk from Africa, whose nests are often coated with the webs of colonial spiders.
Other ‘odd’ species that are difficult to classify include the wonderfully-named Plumbeous Hawk, the Grasshopper Buzzard and the Semiplumbeous Hawk, also the Grey Buzzard-Eagle from South America, also known as the Chilean Eagle or the Blue Chilean Eagle (which has recently been reclassified as a buteo or buzzard), and the Harris’ Hawk. Most of these don’t really fit into either the accipiters or the buteos (true buzzards).The Harris’ Hawk is a very unusual raptor because of its social breeding system. In the most northern part of their range in the western states of the USA, they will live, breed and hunt together in family groups, rather than the traditional monogamous pairing. They do this in their range in South America as well, but it is not as well documented. This kind of cooperative breeding is fairly rare amongst other raptor species, although there are a few others that are also well-known for this type of social behaviour, including the Galapagos Hawk, Madagascar Fish Eagle, Bearded Vulture, Pale Chanting Goshawk and the Red-throated Caracara.
The accipiters are the largest genus (related group) in the diurnal bird of prey group – 49 currently recognised species to date. The Variable Goshawk from Australasia has the greatest number of subspecies – currently 20 are known. The accipiters or true hawks, such as the Eurasian Sparrowhawk and the Goshawk, are mainly forest living birds. They vary in size from the African Little Sparrowhawk weighing between 74 – 105 grams, to the Northern Goshawk, which can weigh over 1500 grams. They almost all have short rounded wings, long tails used for steering and braking, and usually yellow or orange eyes, although not always. The goshawks have thick strong legs and powerful feet, the sparrowhawks tend to have thin, fine legs, long toes and needle sharp talons.
The buzzards or buteos are a large genus or group, and probably one of the most commonly seen in many parts of the world. In the UK, over the last decade the Common Buzzard, also known as the Eurasian Buzzard, which used only to be found in Wales and the west side of Britain, has increased dramatically and now can be seen soaring and gliding over much of Britain’s farmlands. Previously it had been badly affected by the reduction of rabbits which were killed by the rabbit disease, Myxomatosis. If you see a large bird about two feet high either sitting on the ground or on a post you will most likely have seen one of the buzzard or buteo family. With large broad wings and a short tail, they will sit for hours, perch hunting, or will soar on thermals or on ridge currents. They hunt mainly small mammals, reptiles and feed on a great deal of carrion. In North America, one of the most commonly seen raptors is the Red-tailed Hawk, which is also a buteo.
The final group in this family is the eagles. There are currently 75 recognised eagle species, some well known, some not so well known, some common and some quite rare. One of the most threatened is the Philippine Eagle – a huge forest eagle that has had much of its habitat destroyed. Another huge forest eagle is the Harpy Eagle from South America, which also suffers from habitat loss and also direct persecution. One of the most widely distributed of all the eagles is the Golden Eagle, found in many parts of the Northern Hemisphere.
Many of these large birds live in the mountains and open plains of the world. But some have evolved to become more hawk-like and live in the woods and forests of the world. The largest of these is the African Crowned Eagle, and the smallest is Wallace’s Hawk Eagle from South East Asia. There are eight hawk eagle species that can be found in South East Asia, however, like the Philippine Eagle, they are under threat if the primary forests around the world continue to be felled at the rate they are being lost today.
This species is the only one in its group and has always been placed in its own individual family. It is a very specialist feeder and although there are other diurnal and nocturnal birds of prey that catch and eat fish, very few specialize quite as much as the Osprey which feeds almost exclusively on live fish. The Osprey is found on every continent except Antarctica, living by inland waters, estuaries and coastal areas. Surprisingly, although the species is so widespread, there is little variation in colour and size between birds in different regions. They have a pronounced angle or crook to their wing shape when they fly, giving them a distinctive ‘M’-shaped flight profile, which makes them relatively easy to identify.
Some Osprey populations migrate, and some are more sedentary. Interestingly, the young birds don’t migrate back north for two to three years, which makes sense as they are not old enough to breed until that point in their lives. When they do return, they often re-use traditional nest sites or they build large new nests and lay one to three eggs. When hunting for fish they either snatch fish from the water’s surface, barely getting their feet wet, but they can also drop right into the water, feet first, sometimes disappearing almost completely under water.
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The Secretary Bird
Like the Osprey, this bird is the only one in its family and it is fairly obvious why – there is no other bird of prey that looks like it or behaves in the same way. Standing three feet high with long legs like a heron, this odd bird is found only in Africa below the Tropic of Cancer. It spends most of its time on the ground walking through the grasslands and bush looking for things to eat. It is best known for its habit of killing snakes by stamping them to death, however it actually catches relatively few snakes and the bulk of its quarry is grasshoppers and locusts. It will also eat other large insects, small mammals, birds (especially young ones), eggs and the occasional tortoise. The Secretary Bird is a capable flier, with a wingspan of seven feet, and its long legs dangle out behind while it flies. It breeds at the end of the dry season in Africa so it can take advantage of all the food around during the wet season to feed its young.
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Nocturnal Birds of Prey (Owls)
The Barn Owls
Probably the best known of all the owls is the Common Barn Owl, which is found throughout the world on every continent except Antarctica, and like most species that has such a wide distribution, it varies a great deal. For example, the Common Barn Owl found in North America is considerably larger than the European Common Barn Owl, and the Common Barn Owl in the UK has a white front whereas the ones from continental Europe are dark breasted. Of all the owls, all the barn owl species have the most marked facial disc, giving them a distinctive heart-shaped look. There are 15 different species of barn owls, some of which are listed as rare, mainly because their habitat is being lost. Like all the owls, they use their hearing as much if not more than their eyesight to locate their prey. It is said that a Common Barn Owl can locate a mouse in zero light – i.e. in pitch darkness using only its hearing to locate and catch the moving mouse.
Also in this family are two species of owls called bay owls. One comes from the Far East and one from Africa – there is very little known about the African bird apart from one dead specimen and more recently, some owls have been heard vocalising. The Oriental Bay Owl is better known; it is smaller than most of the barn owls and the facial disc is more square than heart- shaped, it has huge dark brown eyes which points to it being extremely nocturnal. These forest-dwelling owls are a bit bigger than the European Little Owl.
The Rest of the Owls (also called Eared Owls or Typical Owls)
All the other species of owls are put under one family name, although they vary a great deal and are divided into two sub families.
This group contains very small owls, such as the Indian Scops Owl and the European Scops Owl, which only weighs about 60 grams. These scops owls form the biggest group with 68 species currently recognised. Also in the same sub-family are the eagle owls, which are large to very large owls, all with feathered ear tufts. The biggest of all is the Eurasian Eagle Owl; females can weigh up to 10lbs in weight. Very similar, but a little smaller, is the Great Horned Owl from both North and South America. Africa has a large eagle owl called the Milky Eagle Owl (or Giant Eagle Owl), although it is smaller than the Eurasian Eagle Owl. Australia has no eagle owls.
The fishing owls look similar to the eagle owls although they tend to have longer ear tufts, but they don’t have feathered legs and toes, as they drop their feet into the water when fishing, thus their legs and feet are kept drier. Blakiston’s Fish Owl is thought to be the largest of all the owls, although it is probably very close in size to the Eurasian Eagle Owl.
The tiniest of all the owls are the pygmy owls. The Least Pygmy Owl has a very descriptive scientific name – Glaucidium minutissimum. All the hawk owls come under the same grouping but these are further divided by region. There is one hawk owl species found in the Northern Hemisphere, the Northern Hawk Owl, found in parts of North America, Europe and Asia. All the other species of hawk owl live in the Southern Hemisphere. As their name denotes, they have a hawk-like build with the same long tail that typifies the hawks. The Northern Hawk Owl flies in a very hawk-like manner and will happily hunt in the full daylight during the summer months. The Australian Ninox owls are all hawk owls in this group.
Unusually, Australia has only two genera of owl species; all their owls are either barn owl species (Tyto) or belong to the Ninox genus. Some are quite odd in that the males are bigger than the females – which is uncommon – usually in raptors females are larger than the males. The female Sooty Owl, however, exhibits a massive size difference from the male – so different that some of the smaller males were once thought to be a different species altogether.
This is the other sub-family in the owl group and includes the Tawny Owl, Barred Owl, Great Gray Owl and the beautiful Asian Wood Owl, known collectively as the wood owls. Also in this group is the Short-eared and Long-eared Owl, which reside in large parts of the Northern Hemisphere. The Fearful Owl from the Solomon Islands is a relatively small owl, but with a very powerful beak and huge feet for its size; it is said to be as powerful as a Great Horned Owl.
The last of the owls in this sub-family are four small, high-forest owls, including the Boreal Owl, also known as Tengmalm’s Owl, which inhabits the cool forests of Eurasia and North America.
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