668 Birds. 



an enemy. It is stated by your correspondent (Zool. 498), that " the feet are the 

 instruments by which they are enabled to remain in this state of submergence ;" and 

 that " they lay hold of some weed or flag, and by the purchase so obtained, resist the 

 tendency of the water to buoy up their body." But as this often happens in deep wa- 

 ter, and where there are no weeds or flags whatever near the surface, to enable them to 

 do so ; this explanation appears far from being satisfactory, and more particularly so, 

 as the same power of " submergence " is possessed by all the duck and diver tribes, 

 the formation of whose feet totally prevents their acquiring any purchase or hold upon 

 weeds, even if there were any within their reach. But I venture to suggest that the 

 power of submergence is derived from another power possessed by the various classes 

 of waterfowl, as well as other birds ; namely, that of being able to expel at pleasure 

 the air within the various cavities of the body, and which, when the air-cells are filled 

 with air, is the cause of the buoyancy and resistance to the water of the former class, 

 and enables them to float without any effort or exertion to themselves. Every observer 

 of the habits of birds must no doubt have been frequently struck by seeing a wild duck, 

 while endeavouring to conceal her young brood from the obtrusive gaze of any passing 

 stranger, and at the same time of avoiding detection herself, gradually sink and lower 

 her before plump and full looking body, to very nearly a level with the water, leaving 

 only the head and a small portion of the upper part of the body visible above the sur- 

 face ; and thus partially concealed from view, the old duck will coast along the margin 

 of the pool, and turning to account every root or other projection likely to afford shel- 

 ter, will silently place herself in a position of safety. And when thus withdrawn from 

 observation, and surrounded with her little timid progeny, from time to time she gent- 

 ly admonishes them that there is danger abroad, until she conceives that it has passed 

 away, and all is safe again. If, during this period of cautious concealment, the old 

 duck is carefully watched ; or when it happens that a teal, wigeon, or any other kind 

 of wild fowl, which has been w T inged and has dived, on raising its head only above the 

 surface of the water, where it will frequently remain for a long time so submerged; — 

 as soon as the apparent danger is removed, they will then be seen gradually to resume 

 their former perfect size, and without the slightest effort, will raise themselves to their 

 original height and fullness on the surface of the water ; and as easily and speedily 

 depress and sink the body if they again perceive the former cause of fear is renewed. 

 Immediately also upon a tame duck, or any other water bird, where there exists no 

 cause of alarm, arising to the top of the water after diving, it does not instantly assume 

 its full plump form, but some seconds intervene before it is able to acquire it complete- 

 ly. And I cannot but feel assured, from having often watched the various kinds of 

 golden eye, and others of the diver as well c^ of the duck tribe, that having previously 

 expelled the air within the body, they are thereby the better enabled, with the aid of 

 some positive exertion also on their parts, to dive and keep under water; and that up- 

 on their again returning to the surface, some little time is necessary before the various 

 air-cells are sufficiently refilled by the freely restored respiration to give the bird its 

 original fullness and height above the water. I have never had the opportunity of 

 seeing this exemplified in swans and geese, but judging from a similar effect in cor- 

 morants, I have little doubt the same result would be perceived in all other birds whose 

 habit it is to dive. I apprehend that without this power of ejecting or getting rid of 

 the buoyancy caused by the air within the body of all descriptions of birds, — that a 

 hawk, or any other bird, desirous of making a swoop, or sudden downward descent, 

 would not be able to effect its object so easily, unless the internal air was first expelled 



