148 THE BIOLOGY OF BIRDS 



to be mainly the male's work, the bird uses its laterally com- 

 pressed bill or " coulter-neb " and also its feet which, 

 though webbed, bear strong nails. 



It is a great pleasure to watch the movements of a Little 

 Grebe or Dabchick on a quiet reach of the river. Rising 

 upright out of the water, it turns a somersault so quickly 

 that our eye cannot follow what happens. It dives head 

 foremost and reappears somewhere else. It is always doing 

 this, " quicker than a shot," for it feeds usually on very 

 small animals, and it takes many a pickle to make a mickle. 

 Under water, it can use its wings as well as its chestnut-leaf 

 feet. It is a very quiet creature, elusive to a degree, with an 

 extraordinary power of self-effacement. Without any splash 

 it seems able to submerge itself, we do not know how. And 

 the training of the young birds by the mother is most 

 admirable. 



{d) Adaptations of plumage to aquatic life may be well 

 illustrated by the thick soft covering on the under surface, 

 reaching a climax in grebes. The feathers are concave 

 towards the body, they overlap those behind them, they are 

 well greased, they include much air in their capillary spaces ; 

 nothing could be better adapted to conserve the precious 

 animal heat in the cold water. Moreover, beneath the 

 skin in which they are implanted there is a thick layer of 

 fat. 



In many of the ducks and geese (Anseriformes) the 

 contour feathers on the underside below the wing are 

 disposed, as Heinroth has described in detail, almost at 

 right angles to the long axis of the body, so that they form 

 a sort of pocket for the wings. This is important, for it 

 prevents the wings from becoming wetted ; and it is 

 interesting to notice that the development of the pocket is 

 more perfect in the Diving Ducks, which have not to keep 

 flapping their wings dry as non- diving ducks do. It is 

 very interesting, as Hilzheimer points out, that birds Hke 

 cormorants which only enter the water occasionally have to 

 spend a good deal of time drying their wings when ashore, 

 whereas more thoroughly aquatic birds, which remain 



