BLACK-BILLED CUCKOO 73 



The first birds Dr. Clarke observed being imposed upon were a pair of chipping 

 sparrows, who raised the young cuckoo at the expense of the family. 



Next came a pair of yellow warblers, whose prot(!:g6 soon crowded out the 

 legitimate occupants of the nest. They were raised from the ground and placed 

 within reach, but the big boy required all the attention of the foster-parents, 

 and the others died. During the whole period, the old cuckoo was always to be 

 found flitting about in a restless manner, as if she had some doubt in regard to 

 the ability of the warblers to take care of her child. 



The third case was another pair of chipping sparrows, in whose nest the cuckoo 

 was observed sitting, and from wliich she did not move till the observers almost 

 touched her. The result was the same as in the other cases. The young 

 cuckoo threw the sparrows out as soon as he had sti-ength to do so. 



Eggs of the black-billed cuckoo have also been found in nests of 

 the wood pewee, cardinal, cedar waxwing, catbird, and wood thrush. 

 Under the preceding species will be found a note, published by J. L. 

 Davison (1887), describing the finding of a nest occupied by a robin, 

 a yellow-billed cuckoo, and a mourning dove. Bendire (1895) pub- 

 lished an almost identical account of such a remarkable occurrence, 

 on the authority of the same observer, but with the black-billed sub- 

 stituted for the yellow-billed cuckoo. It seems hardly likely 

 that such an unusual happening could occur with both species in ex- 

 actly the same way, and leaves us in doubt as to which species of 

 cuckoo was involved. 



Eggs. — The black-billed cuckoo commonly lays 2 or 3 eggs; sets of 

 4 or 5 may sometimes be the product of a single pair; but the larger 

 numbers that have been found in their nests, 6, 7, or even 8 eggs, were 

 probably laid by two or perhaps three females, as these birds are 

 notoriously careless about laying in each other's nests. Bendire 

 (1895) says: "The eggs of the Black-billed Cuckoo are more nearly 

 oval than elliptical oval, and shorter and rounder than those of the 

 Yellow -billed Cuckoo, and much more deeply colored. Like these, 

 they are unspotted; the shell is thin and fine grained, with little or 

 no gloss. Their color is diflficult to describe exactly, varying from 

 nile blue to pale beryl green, and occasionally the shell shows a de- 

 cidedly marbled appearance, caused by different shades running into 

 each other. * * * Aside from their deeper color, they are also 

 readily distinguished from eggs of the Yellow-billed Cuckoo by their 

 smaller size." 



Eggs that I have seen in collections I should describe as "pale 

 glaucous green," "dull opaline green," or "microline green" and vary- 

 ing from oval to elliptical-oval. Some of these, as well as some of 

 those included in the following measurements, may be yellow-billed 

 cuckoos' eggs, as the two are probably not always recognizable with 

 certainty. The measurements of 54 eggs, presumably of this species, 



178223—40 a 



