106 BIRDS THROUGH AN OPERA-GLASS. 



poses upon its brothers in the same systematic 

 manner. It employs subtle measures, however, 

 and the result of its work is much worse than that 

 of the kingbird. Audubon says, " Like some un- 

 natural parents of our own race, it sends out its 

 progeny to be nursed." Coues says of its habits : 

 " Like the European cuckoo, it builds no nest, 

 laying its eggs by stealth in the nests of various 

 other birds, especially warblers, vireos, and spar- 

 rows ; and it appears to constitute, furthermore, 

 a remarkable exception to the .rule of conjugal 

 affection and fidelity among birds. A wonderful 

 provision for the perpetuation of the species is 

 seen in its instinctive selection of smaller birds as 

 the foster-parents of its offspring ; for the larger 

 egg receives the greater share of warmth during 

 incubation, and the lustier young cowbird asserts 

 its precedence in the nest ; while the foster-birds, 

 however reluctant to incubate the strange egg 

 (their devices to avoid the duty are sometimes 

 astonishing), become assiduous in their care of 

 the foundling, even to the neglect of their own 

 young. The cowbird's egg is said to hatch sooner" 

 than that of most birds ; this would obviously con- 

 fer additional advantage." 



The birds upon which the cowbird imposes 

 sometimes build a second floor to their houses 

 when they find the big stranger egg in their 

 home, and a case is given where even a third story 

 was built. The cowbird spends a large share of 



