Vultures are not only charistmatic birds in the popular imagination, but are strikingly convergent, especially regarding feeding types...

In the popular imagination amongst the birds the vultures score high. With their repulsive scaly necks, powerful beaks and large size these carrion-eaters certainly attract attention. They are also strikingly convergent.  Both are called vultures, but those from the Old World are not closely related to those in the New World. Oddly enough the New World vultures are known in the fossil record from the Old World, but in due course went extinct so that now they are restricted to the Americas.

Scavenging types

In addition to the general morphological similarities there are interesting and specific convergences in types of feeding. In essence there are different ways of dealing with a carcass.  In each group three main varieties are identified, each with a characteristic skull shape and beak type. They are the rippers (wide skull, strong beak) that tear at the flesh; the gulpers (narrowest skull, beak of intermediate strength) that plunge into the recesses of the carcass in pursuit of soft viscera; and scrappers (narrow skull, weak beak) that feed on the scraps around the carcass.

Old World vulture ecomorphs

The Old World vultures belong to the accipitrids, a group that also includes the eagles, kites and hawks. Interestingly even within the accipitrids the vulture ecomorph has evolved twice, in the Aegypiinae and Gypaetinae. The diphyletic nature of the Old World vultures was largely recognized on the basis of molecular data, notably in a study of accipitrid mitochondrial and fibrinogen genes (H.R.L. Lerner and D.P. Mindell  Molecular Phylogenetics and Evolution 37, 327-346; 2005). Other convergences identified by Heather Lerner and David Mindell include that between the palmnut vulture, which primarily eats nuts and fruit, and the Sea-eagle Haliaaetus .

Tool use in vultures

Among the Aegypiinae vultures we find the Egyptian vulture (Neophron percnopterus), a species important for providing yet another example of tool use in birds. It uses stones to crack open ostrich eggs, a very rich food resource, and has also been observed using twigs to sweep wool when gathering nest material.

Cosmetic colours

Application of colour to the body is a well-developed habit in humans, cosmetics being used to enhance attractiveness, intimidate or for camouflage. Surprisingly, the bearded vulture  (Gypaetus barbatus) has also been found to deliberately apply colour, in the form of a dark orange ‘ochre’. Bearded vultures typically have red-orange coloured head, neck and chest regions, from rubbing their plumage in iron-oxide rich soils. Colouration is more intense in females than males and also more striking in older vultures. It has been suggested that this bird cosmetic may provide a status signal, reducing conflict among females, who are larger and more aggressive than the males.