GENERAL HABITS 195 



bill comes and drags it out. When not feed- 

 ing in company the male digs his prey out 

 of the decayed wood, whilst the female probes 

 the nooks and crevices for hers. This pecu- 

 liarity is an example of what is called sexual 

 dimorphism, a phenomenon of which we shall 

 say more presently. 



It is a somewhat remarkable fact that very 

 similar modifications of the bill are found in 

 distantly related groups of birds where the 

 same kind of food is sought. There is, for 

 instance, a very strong resemblance between 

 the bills of the Divers, Grebes, Herons, and 

 Storks all possessing beaks more or less spear- 

 shaped, and adapted most beautifully to seizing 

 slippery fish. But, on the other hand, we also 

 find extraordinary divergence in the shape of 

 the beak in some members of the same order. 

 What, for instance, could be more unlike than 

 the sharp spear-like bill of the Heron and the 

 flat spoon-shaped beak of the Spoonbill ? Dif- 

 ferent food, or different methods of securing 

 it, explain the curious variation ; for one bird 

 stands by the water-side and transfixes the fish 

 as they swim unsuspectingly by, whilst the 

 other sifts the mud and water, moving the flat 

 bill from side to side in a half circle. The 



