two months. During this time probably from eight to twelve eggs are laid 

 by each female, or the equivalent of two broods, and I believe that several days 

 elapse between the laying of each egg. It is not likely, and this is very fortunate 

 indeed, that more than half of these eggs are hatched, as some are occasionally 

 dropped in old or abandoned nests, or even on the ground ; others are laid in 

 just completed nests which the rightful owner abandons when it sees the 

 parasitic tgg. 



When the Cowbird is ready to lay, she quietly leaves her associates and 

 begins to search for a suitable nest, usually selecting one of a species smaller 

 than herself, but if such a one is not readily found, a nest of a larger bird will 

 answer, especially if the full complement of eggs has not been deposited in it. 

 She does not forcibly drive the owner from the nest, but watches her oppor- 

 tunity to drop her egg in it when the nest is unguarded. 



It is not unusual to find some of the eggs of the species imposed on, thrown 

 otit of the nest to make room for those of the parasite, nor to find minute 

 punctures in the shell of some of the remaining eggs. This is possibly done 

 on purpose by the Cowbird with her beak, to keep the eggs from hatching, or 

 with her sharp claws while sitting on the nest and depositing her own egg. I 

 am inclined to attribute this puncturing to the latter cause, but there is no doubt 

 that the Cowbird sometimes throws the rightful owner's eggs out of the nest 

 purposely, to increase the chances of its young for -food and growth. 



It is astonishing how many different kinds of birds are thus imposed upon by 

 the Cowbird. A list of ninety species of these victims has been prepared. Among 

 these the nests of the phoebe; song sparrow, towhee, indigo bunting, ovenbird, 

 and yellow-breasted chat, seem to be most frequently selected, and these usually 

 contain also more of the parastic eggs than a majority of the others. 



The egg of the Cowbird usually hatches in from ten to eleven days, gen- 

 erally in advance of those of the foster parents, and the growth of the young 

 interloper is rapid. The observations made by Mr. ]\I. A. \\'hite upon the egg 

 of a Cowbird in the nest of the chipping sparrow illustrate this life history. 



About the nineteenth of June Mr. Cowbird emerged from his prison walls, 

 large and vigorous. A day later a little sparrow came forth from his delicate 

 shell, but much smaller and exhibiting less strength than his foster brother. 

 The other egg of the sparrow failed to hatch. 



The daily increase in size of the Cowbird was surprising, while his younger 

 companion seemed rather to diminish than to enlarge, until finally at the end 

 of three days the sparrow died — evidently for want of food as the Cowbird, 

 being larger, devoured everything that came in contact with his capacious mouth. 



The untimely end of the rightful heir was but gain to the usurper as he 

 now received the whole attention of the parent birds. Nature having now, 

 at the early age of seven days, provided him with a respectable dress he was 

 no longer contented to remain within the nest, and he betook himself to the 



451 



