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An introduction to Birds of Prey

Buzzards (US Hawks)	Eagles	Falcons	Harriers	Hawks
Kites	Owls	Vultures (US Buzzards)	Others	Raptor Anatomy

Raptors are one of the most successful and widely distributed bird groups in the world. Raptors are found on every continent (except Antarctica) and in virtually every habitat type on the planet.

There are currently two main groups or orders: Falconiformes (diurnal or daytime raptors) and Strigiformes (owls). Their variety is stunning, with more than 300 species of diurnal raptors and more than 200 species of owls.

Before going into the various groups, what is a 'raptor'? What does it mean?
The word raptor comes from a Latin word, rapere, meaning "to seize, snatch, tear away; to plunder a place". It is a general term used to cover all birds of prey. Given the highly predatory nature of many birds in this group, it is a very appropriate word to use.

There are four main orders:
1) New World Vultures (Catharditae in the order Ciconiiformes)
2a) Hawks and relations (Accipitridae in the order Accipitriformes)
2b) Ospreys (Panionidae, also in the order Accipitriformes)
3) Secretary Birds (Sagittaridae,alone in the order Sagittariiformes)
4) Falcons and relations (Falconidae in the order Falconiformes)

The owls (Strigiformes) can be divided into two families:
1) Barn Owls and relations (Tytonidae)
2) Typical or other owls (Strigidae)

These families are broad classifications, and there are several distinct characteristics that help with identifying to which group a particular bird belongs. Most of the differences are general and not definite. It is sometimes very difficult to determine to which family a bird might belong. There are some buzzards which on the surface appear very much like hawks, and vice versa. Additionally, taxonomists will often make a distinction between two species which appear, on the surface, quite similar. There may, however, be many internal differences, usually in bone structure or other features, or in differences in voice. Modern DNA analysis has served to correct some apparent misconceptions inherited from less precise science, but this is still a young area of study and different authorities occasionally produce conflicting interpretations of the same evidence.

A feature that is common with many species of raptor is that females are larger than males. This is called reverse sexual dimorphism and, as a general rule, the more predatory the species, the greater the size difference. In some species, the females can be half as big again as their male counterparts. Conversely, where a species is not an aggressive hunter, there is little difference. In fact, with some vultures, the males are slightly larger than the females.

Many people believe raptors to be solitary and aggressive. This is not entirely accurate. Birds of prey tend to be monogamous - they mate for life. This is particularly the case with large eagles, who will also often return to use the same nest for many years. Mates will sometimes preen each other, and a number of species are highly gregarious. The notion of raptors being fierce and without compassion no doubt stems from the fact that many are exceptionally good at catching their prey. However, the same raptors are remarkably gentle with their offspring. As Shakespeare once said, `No beast so fierce, but knows some touch of pity'.

Birds of prey are well known for their exceptional eyesight. This is partly due to the relatively large size of the eye. Pound for pound a European Buzzard, for example, has eyes roughly fifty to eighty times larger than an average human. During the day, sensors called cones (located at the back of the eye) pick out sharp contrasts, colour and detail. The cones are concentrated into what is called a fovea. Birds of prey have two foveae - areas of image resolution - in each eye. One is for lateral vision, the other for forward vision. When working in conjunction, they provide an extraordinary level of detail resolution. Outside the foveae, raptors have nearly twice the detail resolution of humans. In the foveae themselves, they can have anywhere between four and eight times the resolution of humans. These estimates are based on the number of cones per square millimetre found in the eyes. Based on this, raptors may well have the most detailed visual acuity of any creature on the planet.

Birds of prey can live to great ages. Some large eagles and vultures have been known to live in captivity for up to 50 years or more. In the wild, however, these maximum ages are reduced significantly. Additionally, a large number of raptors will not survive their first year. This can be due to difficulty in learning to hunt, hard winters, predation from other species or disease. In captivity, most of these limiting factors are removed, and this is why life span can be doubled or sometimes even tripled. In general, size is a good indicator of potential life span. The larger raptors tend to live longer, and will also take longer to reach adult plumage. Some of the larger species may not reach adulthood until they are six, seven or even 10 years old.

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