224 BRITAIN^S BIRDS AND THEIR NESTS. 



as eleven or twelve days. Now the incubation periods of 

 the foster-parents are usually from thirteen to sixteen days 

 in length, so that the Cuckoo"'s egg hatches before or 

 about the same time as the others, if deposited early in 

 their incubation. And this is generally the case. If the 

 Cuckoo''s egg is laid before the others the nest may 

 be deserted ; if long after, the young Cuckoo may find 

 itself unable to remove its rivals and to receive the 

 great quantity of food which it needs. But if the egg 

 is laid at the right time, the young bird has only to 

 cope with eggs and very small nestlings. These it 

 ejects from the nest by clambering backwards up the 

 side, pushing before it an egg or chick resting in the 

 hollow with which its back is specially provided. This 

 hollow fills up after some days, and with it disappears 

 the instinct of ejection, for the Cuckoo then makes no 

 attempt to remove anything that the curious observer 

 may place in the nest. But in the ^rlier stage the 

 young bird will continue, till exhausted, to throw out 

 the eggs which may be replaced. Two Cuckoos in one 

 nest naturally have a battle-royal, probably ending in 

 the ejection of the younger. This may occur through 

 coincidence in the choice of two parent Cuckoos, or 

 through lack of a sufficient supply of suitable nests for 

 one. Three Cuckoos'* eggs in a single nest have been 

 recorded. 



At first the young Cuckoo is blind and naked, and 

 helpless and inactive except for its ejecting feats. For 

 some three weeks it remains in the nest, and during 

 this period and for some time afterwards it is zealously 

 tended and fed by its foster-parents. Their parental in- 

 stincts seem to be satisfied by this, and they do nothing 

 for their own young — left to perish miserably outside. 

 There is something pathetic about the picture — birds 



