606 BIRDS* 



it of various sizes, from that of a pea to that of a small nutmeg. 

 It seems to be composed chiefly of horse-hairs, and from the resem- 

 blance it bears to the inside covering of the nest, I conceive the bird 

 swallows it while a nestling. In the stomachs of old cuckoos, I have 

 often seen masses of hair ; but these had evidently once formed a 

 part of the hairy caterpillar, which the cuckoo often takes for its 

 food. 



There seems to be no precise time fixed for the departure of 

 young cuckoos. I believe they go off in succession, probably as 

 soon as they are capable of taking care of themselves ; for though 

 they stay here till they become nearly equal in size and growth of 

 plumage to the old cuckoo, yet in this very state the fostering care 

 of the hedge-sparrow is not withdrawn from them. I have fre- 

 quently seen the young cuckow of such a size, that the hedge-spar- 

 row has perched on its back, or half-expanded wing, in order to 

 gain sufficient elevation to put the food into its mouth. At this 

 advanced stage, I believe that young cuckoos procure some food 

 for themselves : like the young rook, for instance, which in part 

 feeds itself, and is partly fed by the old ones till the approach of 

 the pairing season. If they did not go off in succession, it is pro- 

 bable we should see them in larger numbers by the middle of 

 August ; for, as they are to be found in great plenty*, when in a 

 nestling state, they must now appear very numerous, since all of them 

 must have quitted the nest before this time* But this is not the 

 case ; for they are not more numerous at any season than the parent 

 birds are in the months of May and June. 



The same instinctive impulse which directs the cuckoo to deposit 

 her eggs in the nests of other birds, directs her young ones to throw 

 out the eggs and young of the owner of the nest. The scheme of 

 nature would be incomplete without it ; for it would be extremely 

 difficult, if not impossible, for the little birds, destined to find suc- 

 cour for tine cuckoo, to find it also for their own young ones, after 

 a certain period : nor would there be room for the whole to inhabit 

 the nest. Phil. Trans. Abr. vol. x. 



The following observations of Dr. Darwin, however should seem 

 to disprove the general doctrine, that the cuckoo never builds a nest, 

 incubates its eggs, or rears its young. 



* I have known four young cuckoos in the nests of hedge-sparrows, in a sma?l 

 paddock, at the same time. Orig. 



