THE PERFECT INCUBATOR 



both thin and strong. This cup is surrounded by a thick 

 coating of grass, bents, roots, and similar materials. 



Consider for a moment what an excellent arrangement it 

 all is for incubating the eggs and keeping the young birds 

 warm and snug : the impervious lining, through which 

 neither wind nor rain can penetrate; the stout, closely 

 woven wrapper which keeps out the cold; could anything 

 be better? Nothing is wanting to complete the incubator 

 except a radiator of some kind, and a lid to prevent heat 

 escaping at the top. Well, the parent bird provides 

 these ; its own warm body is at once both radiator and lid. 

 When sitting on the nest, the wings are spread a little so 

 as to cover the whole cavity, and thus every requirement is 

 satisfied. 



The need for solidity and warmth is therefore beautifully 

 provided for in these nests ; but there is still another point 

 to notice in their construction. The inner surface of the 

 cup is made smooth and soft, and in their method of 

 accomplishing this the two birds differ. The blackbird 

 lines the whole cavity with a layer ot very fine grass, cover- 

 ing the mud wall so completely that it is entirely hidden. 

 The thrush, on the other hand, has resort to a process of 

 which no other bird possesses the secret. Tiny fragments 

 of dead wood are covered with saliva, and this curious com- 

 position is spread in a thin layer over the lining of mud or 

 cow-dung, forming a smooth, elastic surface. It is almost 

 as if the bird laid over the floor of its little chamber a 

 covering of cork carpet. 



Similar as the nests of these two birds are in many 

 respects, they are at once distinguishable by the nature of 

 the lining ; and there can be no mistake as regards the eggs, 

 as every boy knows. 



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