Nesting Habits of Cuckoo. 41 
Wagtail; but, on the other hand, and as if to caution us against 
forming a hasty judgment, there is a Cuckoo’s egg very similar 
to that in the Yellow Wagtail’s nest, in the nest of one of the 
Dartford Warblers, whose eggs it does not at all resemble. 
These two cuckoos’ eggs are quite unlike any of the others in 
the collection, but, as they bear a strong family resemblance to 
each other, and were found in the same district, and in the 
same month, (May, 1860) they were, in all probability, laid by 
the same bird. 
There is a similar and very remarkable family likeness 
bet ween the Cuckoos’ eggs in two of the Robins’ nests, and i 
the Flycatchers’ nest, and one of the separate eggs. These 
four eggs all came from the neighbourhood of Frensham in 
May, 1860, and no doubt were laid by the same bird. 
In one of the Wagtail’s nests is a Cuckoo’s egg which is 
marked something like the egg of a Yellow Bunting. 
The peculiarity in the size of the egg of the Cuckoo is well 
seen in this collection. It is in almost every case rather larger 
than the eggs of the species in whose nest it is placed, but it 
is, nevertheless, very small for the size of the Cuckoo. This, 
no doubt, is due to the very small ovaries of the bird. The 
Cuckoo is rather a large bird, rather larger than a Missel 
Thrush, but its ovaries are only as large as those of the Common 
Brown Wren, and its eggs are not larger than those of the 
Common House Sparrow. The object of this peculiarity in the 
size of the eggs of the Cuckoo can of course only be to assimilate 
them to the eggs of the birds in whose nests they are laid. 
It is now well established that the Cuckoo does not always 
lay its egg in the nest which it selects in the ordinary way, but 
that it often lays its egg on the ground, and then deposits it in 
the nest with its beak. Judging from the places which are 
usually selected by the species whose nests are before us, and 
the character of their nests, there can, I think, be little doubt 
that, in some of them, the Cuckoo’s egg was placed with the 
beak, as above described, but as we have no particulars as to 
how and where these nests were placed, it is, of course, not 
possible to say, with certainty, in what way the cuckoo’s eggs 
were deposited in them. 
