The word raptor is descriptive rather than taxonomic. Raptors are birds with talons instead of claws and large, sharp beaks capable of holding and tearing prey. The other term, bird of prey, is also basically descriptive because this term encompasses two orders of birds and several families. Eagles, hawks and falcons are all birds of prey but so are owls, ospreys and kites. Owls belong to the order Strigiformes while all the rest, plus vultures, belong to the order Falconiformes.
Owls are also known as nocturnal raptors because they are all adapted to hunt at night or in the early hours of dusk and dawn. Owls are divided into two families: the Tytonidae or barn owls with their characteristic facial discs of pale, stiff feathers, and the typical or hawk owls, which belong to the family Strigidae. The common barn owl is found right across the world. The other five species are restricted to the Australasian region. There are two other groups in this family: the grass owls, which live in open grass-covered plains, and bay owls which inhabit wet tropical forests. The facial disks of these birds contribute to their night-time hunting success by funnelling sounds of prey to their ears, which are asymmetrical on their heads, with one higher than the other. The difference in time for the sounds to reach these two ears is used by the owl’s brain to calculate precisely the location of the prey. Even in total darkness, barn owls can swoop down precisely to catch a mouse rustling through the leaf litter. There are 18 species of Tytonids world wide.
The hawk owl family is much larger, with over 200 described species. In common with the tytonids, strigid owls have soft, dense feathers that make them virtually soundless fliers. Most are cryptically colored in browns, creams, greys and buffs so that they are very difficult to spot when roosting during the daytime. They have large, foreward-looking, often bright yellow eyes. Some, like the great horned owl, have prominent ear tufts. Their night vision is far superior to other animals and man and their hearing is also excellent. Their heads can swivel in an almost complete circle, which helps them locate prey while sitting silently.
Hawk owls are found in habitats from the Arctic tundra (Snowy owl) to cool temperate regions in both hemispheres. They can be found in many habitats from deserts to mountains and grasslands but most are woodland hunters. They differ widely in size, from the eagle owl of Scandinavia which can weigh up to 4 kg to the elf owl of Arizona, which is the size of a small sparrow. Prey size varies according to the size of the owl. Eagle owls have been known to tackle porcupines and even small deer, while elf owls eat insects, scorpions and spiders. There are even owls that fish for a living in Africa and Asia.
In contrast, the members of the Falconiformes, from eagles to falcons, hawks to vultures, are diurnal hunters. There are five families of falconiformes: Cathartidae or new world vultures; Sagittariidae, with one species, the Secretary Bird; the Pandionidae, with several species of Ospreys, and the two big families, the Accipitridae (eagles and hawks, kites, old world vultures and harriers) and the Falconidae (falcons).
The Secretary bird is the most different of the group and for this reason is in its own family. It is a large bird with long legs, standing up to 1.2 m high. They live in open country and roost in trees. They are normally found on the ground but can fly well and soar like a vulture. They are confined to Africa, south of the Sahara, where they hunt rodents, insects and snakes.
Ospreys, family Pandionidae, are found around the world except for South America. They are also called fish hawks because that is their favorite food. Their feet are large with powerful talons . The toes have spiny tubercles on the undersides to give a good grip on slippery fish. It cruises above rivers and then plunges in a shallow dive to grab its prey, The grip is so good that the bird has trouble letting go and Ospreys, especially young birds, are sometimes dragged under the water and may drown. Ospreys like to nest in big dead trees with a good view of their territory. They mate for life and help each other look after the young.
The new world vultures, Cathartidae, and the old world vultures of the Accipitridae, are mainly scavengers but they possess the strong beaks and powerful talons of other raptors. Both groups have naked heads but they differ in other respects. New world vultures lack a voicebox and the septum between the nostrils is perforated. New world vultures also do not build nests. Vultures perform an important role as scavengers and clean up detail. Australia has no vultures so eagles perform this function instead.
Besides the old world vultures, the family Accipitridae contains all the eagles and hawks, kites and harriers. There are 235 known species of these diverse and interesting raptors. They occur all over the world except Antarctica and utilise most habitats including the edges of the oceans (sea eagles).
The larger eagles are usually found in open country, with the exception being the Phillipines monkey-eating eagle which lives in rainforests. Small hawks take insects and prey size increases with the size of the raptor. Accipitrids have strong beaks with a strong hook. Being diurnal hunters, their vision is excellent. They also have good hearing although they do not depend on hearing when hunting and most have a poor sense of smell, which is probably good when feasting on carrion. A few have adapted to specialised diets such as the snail eating kite, the honey-buzzards and the fruit eating vulture. Several eagles such as the snake eagle and the serpent eagle target snakes as their main food source.
The final family is the Falconidae, or falcons and caracaras, which contains about 300 known species, some of which are severely threatened or endangered. The caracaras are larger birds with broad wings that do not look like falcons but share some important characteristics, such as the pattern of wing molt and egg shell color. Falcons in general have narrow pointed wings.
Both falcons and caracaras share the common raptor characteristics of hooked beaks and sharp talons. In addition falcons often have a hook or tooth on the beak. Caracaras can be carrion eaters but the rest hunt for live prey, often taking it on the wing. Peregrines, which take birds on the wing, are the fastest fliers in the world. Kestrels tend to prey on small mammals while hobbies take insects. They also have excellent vision and hearing.
This is just an introduction to this important and diverse group of birds. There is much more to be learned about raptors and it is important that we protect them and their habitats. Like lions and wolves, they are top carnivores, predators that depend on their prey and in turn keep prey populations in control and healthy. It would be a much poorer world if we lost any of these amazing birds of prey.
For more information:
http://www.owlpages.com/
http://www.seaworld.org/animal-info/info-books/raptors/scientific-classification.htm
http://www.avianweb.com/accipitridae.html
http://www.encyclopedia.com/article-1G2-3406700532/falconiformes-diurnal-birds-prey.html
