446 Observations on the Cuckoo. 
koo, after it has been hatched nine or ten days, 
will frequently remove a nestling that has béen 
placed in the nest with it, when it will suffer 
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 scapulee downwards is very broad, 
with a considerable depression in the middle, 
which seems formed by nature for the design 
of giving a more secure lodgment to any ob- 
ject that the young cuckoo may be desirous 
of removing from the nest. When it is about 
twelve days old, this cavity is quite filled up, 
and then the back assumes the shape com- 
mon to nestling birds in general. ‘The same 
instinctive impulse which directs the cuckoo 
to deposit her eggs in the nests of other birds, 
directs her offspring to throw out the eggs and 
young of the owners of the nests. The scheme 
of nature would be incomplete without it, for 
it would be extremely difficult, if not impos- 
sible, for the small birds, destined to find 
support for a young cuckoo, to find it for 
their own young ones also, after a certain 
period; nor would there be room for the 
whole to inhabit the nest. 
The eggs of the cuckoo are remarkably 
small in proportion to the size of the bird; 
