CUCKOO. 303 



nine or ten days, remove a nestling that had been placed in the 

 nest with it, when it suffered an egg, put there at the same time, 

 to remain unmolested. The singularity of its shape is well 

 adapted to these purposes; for, different from other newly hatched 

 birds, its back from the scapulae downwards is very broad, with 

 a considerable depression in the middle. This depression seems 

 formed by nature for the design of giving a more secure lodg- 

 ment to the egg of the hedge-sparrow, or its young one, when the 

 young cuckoo is employed in removing either of them from the 

 nest. When it is about twelve days old this cavity is quite 

 filled up, and then the back assumes the shape of nestling birds 

 in general. . . . The circumstance of the young cuckoo being 

 destined by nature to throw out the young hedge-sparrows 

 seems to account for the parent cuckoo dropping her egg in 

 the nests of birds so small as those I have particularised. If 

 she were to do this in the nest of a bird which produced a large 

 egg, and consequently a large nestling, the young cuckoo 

 would probably find an insurmountable difficulty in solely pos- 

 sessing the nest, as its exertions would be unequal to the labour 

 of turning out the young birds. (I have known a case in 

 which a hedge-sparrow sat upon a cuckoo's egg and one of her 

 own. Her own egg was hatched five days before the cuckoo's, 

 when the young hedge-sparrow had gained such a superiority 

 in size that the young cuckoo had not powers sufficient to lift it 

 out of the nest till it was two days old, by which time it had 

 grown very considerably. This egg was probably laid by the 

 cuckoo several days after the hedge-sparrow had begun to sit ; 

 and even in this case it appears that its presence had created 

 the disturbance before alluded to, as all the hedge-sparrow's eggs 

 had gone except one.) . . . June 27, 1787. Two cuckoos 

 and a hedge-sparrow were hatched in the same nest this morn- 

 ing ; one hedge sparrow's egg remained unhatched. In a few 

 hours after, a contest began between the cuckoos for the pos- 

 session of the nest, which continued undetermined till the next 

 afternoon ; when one of them, which was somewhat superior in 

 size, turned out the other, together with the young hedge- 

 sparrow and the unhatched egg. This contest was very remark- 

 able. The combatants alternately appeared to have the advan- 

 tage, as each carried the other several times nearly to the top 

 of the nest, and then sunk down again oppressed with the 

 weight of its burden ; till at length, after various efforts, the 

 strongest prevailed, and was afterwards brought up by the 

 hedge-sparrows. 



To what cause, then, may we attribute the singidarities of 



