LIFE AND BEHAVIOR OF THE CUCKOO 
177 
in one case for three successive years. If two or three cuckoo's 
eggs are found in the same nest they are thus supposed to belong to 
different birds, and no case is known where such eggs were sim- 
ilarly colored. Xewton and others have assumed that in each 
individual the color pattern of the egg is inherited, and that the 
species has become split up into a number of more or less dis- 
tinct groups or gens, each gens laying eggs of a peculiar colora- 
tion. 
9. The list of foster-parents or nurses of the young cuckoo 
has been extended to 1 19 species. (Sharpe.) 
10. The cuckoo, as a rule, lays only in those nests which have 
eggs similar in size and color to her own, a statement originating 
with Aelian in the second century, and revived in a modified 
form by others, especially by Baldamus in the middle of the last. 
While the proper and intrusive eggs are frequently unlike, it is 
maintained by Baldamus and other naturalists who have adopted 
this view, that the cases of similiarity are too numerous to be 
due to chance. Thus, blue cuckoo eggs, which are very rare have 
been found in the nests of the pied flycatcher and red-start 
which also lay blue eggs, but whether found under other condi- 
tions or not seems, at present, to be doubtful. Baldamus devotes 
three colored plates to show the similarit}" of the eggs of Cuculus 
canorus to those of thirteen different nurses. It must be admitted 
that the chances of mistaken identity here are considerable, and 
it seems doubtful if this idea would stand an experimental test, 
which could be easily made, or that difference in color is of suffi- 
cient importance in this relation to be of selective value. 
We should like to know how many of the 119 potential nurses 
of this bird would reject an egg of similar size, whatever its color. 
We know that many birds will accept anything, especially after 
beginning to brood, while others will not. Some will try to incu- 
bate stones or potatoes, and Blackwall mentions the case of a 
hawk which tried to sit on a steel trap, placed in the nest over 
the eggs to catch it by the legs. The uniformly speckled eggs of 
the cowbird (Melothrus pecoris) fare only too well when contrasted 
with the snow-white eggs of the mourning dove, and the nearly 
white eggs of vireos, flycatchers, goldfinches, and bluebirds. 
THE JOURNAL OF EXPERIMENTAL ZOOLOGY, VOL.9, NO. 1. 
