42 THE LIFE OF A BIRD. 



be, to the attacks of many foes ; and they must be 

 so constructed as to offer no striking contrast to 

 the surrounding objects. To this end, the ma- 

 terials harmonize with the colour and character of 

 these objects. In the case of others, no enemy 

 appears to be apprehended, and the materials 

 selected are simply those which are most conve- 

 nient for the purpose the bird has in view. In 

 some cases the architect is compelled to make 

 choice of just such rough materials as the situation 

 it has selected is found capable of affording. In 

 others more favourably circumstanced there is no 

 lack of these things ; and the nest exhibits how 

 carefully and how wisely its ingenious constructor 

 has availed itself of the opportunities placed with- 

 in its reach. We shall find, as we proceed, that 

 the materials employed are, as from these con- 

 siderations it seems natural to expect, singularly 

 various ; while sometimes no materials at all are re- 

 quired, no nest is constructed, but the bare egg lies 

 exposed to the winds of heaven upon the naked rock. 

 It is difficult to proceed systematically in an 

 account of the materials employed in birds'-nests ; 

 but, as far as may be, we shall endeavour so to do. 

 Let us then advert, in the first instance, to those 



