BIRDS. 239 
with the extremities of its wings, as if to be convinced 
that the business was properly executed, it dropped into 
the nest again. Dr. Jenner made several experiments in 
different nests, by repeatedly putting in an egg to the 
young Cuckoo ; -which he always found to be disposed of 
in the same manner. It is very remarkable, that nature 
seems to have provided for the singular disposition of the 
Cuckoo, in its formation at this period ; for, different 
from other newly-hatched birds, its back, from the 
scapulae downward, is very broad, with a considerable de- 
pression in the middle, which seems intended for the ex- 
press purpose of giving a more secure lodgment to the egg 
of the hedge-sparrow or its young one, while 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, the back assumes the shape of that of 
nestling birds in general, and at that time the disposition 
of turning out its companion entirely ceases. The small- 
ness of the Cuckoo's egg, which in general is less than 
that of the house-sparrow, is another circumstance to be 
attended to in this surprising transaction, and seems to 
account for the parent Cuckoo's depositing it in the nests 
of such small birds only as these. If she were to do this 
in the nest of a bird that produced a larger egg, and con- 
sequently a larger nestling, the design would probably be 
frustrated , the young Cuckoo would be unequal to the 
task of becoming sole possessor of the nest, and might fall 
a sacrifice to the superior strength of its partners. Dr. 
Jenner observes, that the eggs of two Cuckoos are some- 
times deposited in the same nest; and he gives the fol- 
lowing instance which fell under his observation. Two 
Cuckoos and a hedge-sparrow were hatched in the same 
nest ; one hedge-sparrow's egg remained unhatched. In 
a few hours, a contest began between the Cuckoos for pos- 
session of the nest ; and this continued undetermined till 
the afternoon of the following day, when one of them, 
