BIRD HOMES 31 



hour was made; on the second day, eight visits; and 

 on the third day, five visits. 



Cowbird. The cowbird never makes a nest of her 

 own, but lays her eggs in the nests of other birds, 

 and these eggs are usually hatched and the young 

 reared by the foster mother. These eggs are gener- 

 ally laid in the nests of birds smaller than the cow- 

 bird, so that when the eggs hatch, the young cow- 

 bird gets more than its share of food and gradually 

 either starves the other nestlings or crowds them out 

 of the nest, so that the rearing of this parasite usu- 

 ally means the destruction of all the other nestlings. 



There are ninety species of birds on which the 

 cowbird has been known to impose in this way. 

 When the young cowbird is full-grown and leaving 

 the nest, it is a most curious sight to see the little 

 foster mother feed her adopted baby. Once the 

 author saw a little mother redstart, a little over 

 five inches in length, following around and feeding 

 a nearly full-grown cowbird nestling, about eight 

 inches long. The little mother seemed quite as con- 

 cerned over her big baby as she would have been 

 over her own offspring. 



There are a number of interesting records showing 

 how the yellow warbler meets this difficulty. When 

 she has found a cowbird *s egg in her nest, she has 

 been known to make another nest on top of the first, 

 thus sealing up the intruder's egg, and then to lay 

 her eggs and rear her young in the second story. 



