216 THE PHILOSOPHY OF BIRDS' NESTS. 



are at hand. Rooks dig in pastures and ploughed fields 

 for grubs, and in doing so must continually encounter 

 roots and fibres. These are used to line its nest. What 

 more natural ! The crow feeding on carrion, dead rab- 

 bits, and lambs, and frequenting sheep-walks and war- 

 rens, chooses fur and icool to line its nest. The lark 

 frequents cultivated fields, and makes its nest, on the 

 ground, of grass lined with Jiorsehair materials the 

 most easy to meet with, and the best adapted to its 

 needs. The kingfisher makes its nest of the lones of 

 the fish which it has eaten. Swallows use clay and 

 mud from the margins of the ponds and rivers over 

 which they find their insect food. The materials of 

 birds' nests, like those used by savage man for his 

 house, are, then, those which come first to hand ; and 

 it certainly requires no more special instinct to select 

 them in one case than in the other. 



But, it will be said, it is not so much the materials 

 as the form and structure of nests, that vary so much, 

 and are so wonderfully adapted to the wants and habits 

 of each species; how are these to be accounted for 

 except by instinct ? I reply, they may be in a great 

 measure explained by the general habits of the species, 

 the nature of the tools they have to work with, and the 

 materials they can most easily obtain, with the very 

 simplest adaptations of means to an end, quite within 

 the mental capacities of birds. The delicacy and per- 

 fection of the nest will bear a direct relation to the 

 size of the bird, its structure and habits. That of the 

 wren or the humming-bird is perhaps not finer or more 



