The Cuckoo. 293 
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 smallness of the Cuckoo's egg, which in 
general is less than that of the hedge-sparrow, is another 
circumstance to be attended to in this surprising transac- 
tion, and seems to account for the parent Cuckoo's 
depositing it in the nest 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 consequently 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 
egg of two Cuckoos are sometimes deposited in the same 
nest ; and gives the following 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 possession of the nest; and 
this continued undetermined till the afternoon of the 
following day, when the one which was somewhat 
superior in size, turned out the other, together with the 
young hedge-sparrow and the unhatched egg. The con- 
test, he adds, was very remarkable; the combatants 
alternately appeared to have the advantage, as each 
carried the other several times nearly to the top of the 
nest, and again sank down oppressed by the weight of 
its burden ; till at length, after various efforts, the 
strongest of the two prevailed, and was afterwards 
brought up by the hedge-sparrow. 
The American Cuckoo, or Cow bird, is quite differ- 
ent in its habits to the European Cuckoo, as it builds a 
nest for its eggs, and hatches its young itself like other 
birds. 
