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This article details the important external morphological characters used in the identification of birds. 

 External Morphology of the Body of a Bird

                                                  Lonchura punctulata (Scaly Breasted or Spotted Munia). Original photo by Omkar Dhavale.

 

Plumage and Feathers -

Feathers are epidermal outgrowths growing only in specialized tracts of skin called pterylae. Pterylosis which is the arrangement of feather tracks (and thus the feathers themselves) is used in bird taxonomy. Plumage refers to the pattern, colour and arrangement of feathers. Recognition of plumage is one of the easiest means of identifying birds from a distance. Plumage can vary between sub-species, between genders and also between breeding and non-breeding seasons in the same individual.

Flight feathers and the shape of the wings and tail -

Flight feathers are feathers that aid in flight. They are long and stiff and although they may be asymmetrically shaped, they are symmetrically paired. On the wings these feathers are called remiges (remix – singular) and on the tail, rectrices (rectrix – singular). These feathers are modified to suit the habit of the bird and thus vary from species to species. In some species these may even be modified for other purposes (such as very long plumes which are used for courtship and display). Coverts are feathers that hide or cover the bases of the flight feathers. The shape of the bird as seen in flight from below or from a distance is also a good indicator of the family of the bird as the outline shape of the bird created by the remiges and rectrixes along with the wings and the rest of the body can be characteristic of particular families.

 

external morphology of a bird

 

 

Beaks or Bills -

The bill of the bird is one of the most important characteristics used to identify the species of the bird. Different orders and families of birds have differently shaped beaks depending upon their feeding habits.

 

 

Feathers and Regions of the Head -

The auriculars are the short fine feathers surrounding a birds ear in and around the ear patch or “cheek” region lying behind the eye. The malar feathers lie between the eye and the throat. The lore is the area between the eye and the bill. These feathers along with various areas on the head such as the crown, forehead, nape, chin, throat etc may be coloured differently to form distinct patches in different species and this helps in their identification.

 

External morphology of the head of a bird

 

 

Feet -

The feet of birds show a lot of variation. There are seven broad categories of modification that bird feet show. Zygotactyl feet are feet where the 2nd and 3rd digits face ahead, while the 1st and 4th digits point backwards (arboreal species such as woodpeckers) . Heterodactyl feet are similar to zygodactyl feet except 3 and 4 face ahead and 1 and 2 point backwards (found in trogons). Anisodactyl feet have the 1st digit pointing backwards and the other three pointing ahead (most common arrangement in birds, seen in passerines). Syndactyl feet are similar to anisodactyl feet but have the 3rd and 4th digit partially joined together (seen in Coraciformes such as kingfishers). Pamprodactyl feet have all four digits pointing ahead though two can be rotated backwards (birds such as swifts). Tridactyl feet have only three digits all pointing ahead (birds such as sanderlings). Didactyl feet have only two toes both pointing ahead (ostriches).

Webbing on the feet is and degree of webbing is also used in identification. Palmate feet are feet where webbing connects only the three front digits (such as the mallard). Totipalmate feet have webbing connecting all four digits (pelicans). Lobate feet have membranous lobes that increase the size of the digits and help the bird swim.

 

birdfeet types

 

 

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References 

Grimmett et al. Birds of the Indian Subcontinent - Publisher - Oxford.