INSTINCT AND INTELLIGENCH 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.® 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 
ean 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. 
