﻿28 ON THE CLASSIFICATION OF BIRDS. 



without any great alteration of the walking attitude. 

 This, in fact, is the reason why the long-legged waders 

 have necks and bills proportionate tf) the elevation of 

 their bodies ; for as the habit of wading and of running 

 requires this great development of foot, so, had they 

 short necks and bills, they could not possibly feed but 

 in a constrained and unnatural position. According to 

 the habits of the bird, so do we find the same structure 

 applied to different uses. Hence, in the swans, and the 

 whole of the duck family (Anatidce), there is great 

 elongation of neck, accompanied by very short feet. 

 Now, were these terrestrial birds, it is obvious that 

 such disproportion of parts would be anomalous ; but 

 they are all aquatic, and without their long necks they 

 would be quite unable to reach the bottom of the 

 waters upon which they swim, and where they are 

 taught to look for their food. A swan or a duck swims 

 along the edge of a reedy stream, and thrusts its long 

 neck into every break, dives to the muddy bottom, and 

 ferrets out among the roots of plants its appropriate 

 food. The length and thinness of the neck makes all 

 these habits perfectly easy, which, but for such an 

 adaptation of structure to its mode of life, would be 

 difficult, if not impossible. Again, all birds which 

 seize their prey from a fixed station, without using their 

 wings in its capture, have also the neck greatly length- 

 ened. The whole family of herons, among the waders, 

 and the aquatic genera of Carbo and Plotus, are ex- 

 amples of this structure. Whereas, when the wings 

 are also used in the capture of the prey, the neck is 

 very short. This opposite extreme is very conspicuous 

 in the whole tribe of Fissirostres , as the swallows, 

 swifts, goatsuckers, &c. ; and in their representatives, the 

 flycatchers, todies, tyrants, &c. It may be taken as 

 an invariable rule, that out of the insessorial and nata- 

 torial order, all birds have their neck and legs of propor- 

 tionate length. 



(37.) The head is generally clothed with feathers ; 

 but in very many birds it is more or less naked. What 



