INSTINCT AND INTELLIGENCE IN BIRDS 93 



" anticipates " the nest. Every one who has given much attention to 

 the activities of birds in the field must have found isolated eggs lying 

 on the ground. Such prize packages are probably more common than 

 we might be led to suppose, for they can not long exist wherever snakes, 

 rodents and other prowling animals abound. 



With most birds the act of prematurely dropping an egg can be 

 only a sporadic or casual variation. Without doubt, in the course of 

 time a proper nest is built; eggs are laid, and the normal cycle is 

 rounded out to completion. It is quite possible, on the other hand, 

 that all such eggs are not immediately neglected, but that they are 

 sometimes carried away, and " concealed " by dropping them in another 

 bird's nest, although we have no observation to support such a view 

 directly. It is known, however, that certain birds, such as the black- 

 billed cuckoo, will upon disturbance remove its eggs from the old nest 

 to a new one or to a place of safety. 6 It is also certain that the prema- 

 ture egg is at times laid direct in another bird's nest, which the in- 

 truder will often strive to possess by force, and may even succeed. 

 Thus, Davidson, who is quoted by Bendire, found a black-billed cuckoo 

 and a mourning dove sitting on a robin's nest together. This nest 

 was in reality double, and contained two eggs each, of the cuckoo and 

 dove, and one of the robin. The cuckoo managed to get possession of 

 the nest before the robin had finished her work, and filled it with 

 rootlets, but the robin held its ground long enough to deposit an egg. 

 The fact that the cuckoo had " filled it nearly full of rootlets " is a 

 very interesting circumstance, for it shows how completely instinct held 

 the reins of action. This robin's nest seems to have served as a site 

 on which the cuckoo strove to erect one of its own. The dove, noted 

 for its strong parental instincts, had evidently come last, and her eggs 

 were the only ones in which incubation had not begun. 



Such a case seems to present us, as in a picture, with one of the 

 steps in the process through which the most remarkable of all the 

 known instincts of birds, that of parasitism, has been brought about. 



Certain cowbirds of the new world and cuckoos of the old steal the 

 nests of other birds, but usually only long enough to deposit an egg of 

 their own, which is left to its fate. If tolerated, as is apt to be the 

 case, the stranger is hatched with the other eggs, and the owner of the 

 nest assumes the role of nurse or foster-parent. If a cowbird, the 

 foundling soon smothers the proper young, and if a cuckoo, it evicts 

 them. The cuckoo seems to react to a contact stimulus of a disagree- 

 able kind, and when from one to three days old, while still blind, it 

 strives to get egg or nestling on its broad, depressed back, and 



•That other species of birds occasionally remove their eggs when disturbed 

 can not be doubted, and they probably do it with their bills. The king penguins 

 of the Antarctic are said to guard their single egg by carrying it in a pouch 

 or fold of the skin, developed in either sex, between the legs. 



