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 tbe 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 ro 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 singularities of 
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