CONCERNING THE CUCKOO 113 



to have acquired their striking appearance as a 

 protection from birds. Strange to say, however, 

 it is these caterpillars of the hairy kind, which other 

 birds leave, which form the staple food of the cuckoo. 

 The bird, by universal consent, is enormously greedy, 

 and it devours great quantities of them. Now, it 

 is pointed out that, as the supply of this food soon 

 fails, the cuckoo is obliged to migrate so early that 

 it would not have time to take upon itself the cares 

 of maternity, and so it has acquired the convenient 

 habit of placing its offspring out to nurse. Unfor- 

 tunately, however, for this theory, there are several 

 difficulties in the way of accepting it as it stands. 

 The habit is said to be found in the Indian species, 

 which do not migrate. The old birds leave us in 

 July and August, but the young remain a month 

 or six weeks longer ; and if they can find food, why 

 not the old birds ? 



Another theory which has its supporters is that 

 the parasitic habit is the result of a peculiarity in 

 the manner in which the cuckoo's eggs are laid. 

 It is now well known that the bird does not deposit 

 her eggs rapidly like most birds, but that an interval 

 of four or five or even eight days intervenes between 

 them. Hence it is said that the cuckoo evidently 

 could not utilize a nest of her own, for the first 

 eggs would be addled or hatched before the last 

 were laid. There are difficulties in the way of this 

 theory too. There are other birds who lay their 

 eggs in the manner of the cuckoo, but without having 

 acquired its parasitic habits. Irregularity in this 

 respect exists doubtless to some extent in many 

 kinds of birds, and in some to a considerable degree. 

 Mr. Cones says of the American species (Coccygus) 

 8 



