216 THE PHILOSOPHY OF BIRDS’ NESTS. 
are athand. 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 wool to line its nest. The lark 
frequents cultivated fields, and makes its nest, on the 
ground, of grass lined with horschatr—materials the 
most easy to meet with, and the best adapted to its 
needs. The kingfisher makes its nest of the bones 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 
