Monday, April 15, 2013

The extreme diversity of Accipitridae

In classification, families range from being pretty well-defined to diverse beyond belief. The family Accipitridae falls into the latter category. Accipitridae includes most species birds of prey, collectively known as raptors. At first glance, the diversity of the family appears to be too great to be supported by anything but morphological; however, karyotypic data has supported the theory that the accipitrids are monophyletic (that is, sharing a common ancestor). Though most of the birds of prey are accipitrids, not all species are included: the secretary bird, owls, New World vultures, and the osprey are all included in families of their own due to genetic differences.

At first glance, raptors may appear to be very similar. To demonstrate just how diverse this family is, I've chosen a representative from each of the subfamilies of Accipitridae. A very special "thank you" to Gareth Monger, who created the following visual. All raptors are to scale, although some of them may be skewed due to odd angles.

Click to embiggen.

1. Bearded vulture (subfamily Gypaetinae) - Also known as the lammergeyer, it feeds on marrow by dropping bones from great heights. It also uses this technique to feed on tortoises.

2. Snail kite (subfamily Milvinae) - The long upper jaw of this raptor allows it to feed almost exclusively on snails, though it will also eat crustaceans and fish as well.

3. Dark chanting-goshawk (subfamily Melieraxinae) - Couldn't find anything particularly unusual about this species. Sorry, folks.

4. Harris hawk (subfamily Buteoninae) - The only raptor to actively hunt in familiar packs.

5. Pearl kite (subfamily Elaninae) - The second-smallest raptor in the world. Preys mainly on Anolis sp. lizards.

6. Black baza (subfamily Perninae) - Captures insects on the wing, or plucks them off of leaves. It has also been observed eating palm fruit.

7. Philippine eagle (subfamily Circaetinae) - Also known as the monkey-eating eagle. It also preys on anything from monitor lizards to hornbills.

8. Steller's sea eagle (subfamily Haliaeetinae) - Feeds mainly on fish, though also hunts waterfowl, gulls, herons, and cranes.

9. African harrier-hawk (subfamily Polyboroidinae) - Its "double-jointed" legs can bend forwards and backwards, allowing it to raid the nest cavities of smaller birds for fledglings.

10. Cinereous vulture (subfamily Aegyptiinae) - The world's largest true raptor. Reported to fly very close to herds of wild sheep, perhaps in order to pick out potential prey.

11. Harpy eagle (subfaimly Harpiinae) - Hunts mostly sloths, though large monkeys are also eaten.

12. Shikra (subfamily Accipitrinae) - Feeds on everything from termites to bats to birds. It often uses metal wire as part of its nest.

13. Verreaux's eagle (subfamily Aquilinae) - A hyrax specialist, though it will also hunt small antelope and other animals.

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