270 BRITISH BIRDS. 



Nature seems to have provided, even in the for- 

 mation of the Cuckoo, for the exercise of this 

 peculiar instinct, for unlike other newly hatched 

 birds, its back, from the scapulae downwards, is 

 very broad, with a considerable depression in the 

 middle, as if for the purpose of giving a more 

 secure lodgment to the egg, or the young bird, 

 while the intruder is employed in removing either 

 of them from the nest ; when about twelve days 

 old, this cavity is filled up, the back assumes the 

 shape of nestling birds in general, and the dispo- 

 sition for turning out any bird or substance placed 

 in the nest, entirely ceases. The smallness of the 

 Cuckoo's egg is another circumstance deserving 

 attention in this surprising transaction ; in size 

 and appearance, it differs little from the egg of 

 the Sky Lark and Titlark, though the disparity of 

 bulk of the birds be very great; in short, every 

 thing conspires, as might be expected, to render 

 perfect the design which is to be accomplished 

 by the seemingly unnatural propensity of this 

 bird. 



When it happens, as it sometimes does, that two 

 Cuckoo's eggs are deposited in the same nest, and 

 are hatched along with those of the Hedge Spar- 

 row's, a contest commences in a few hours between 

 the Cuckoos for the possession of the nest. In 

 one of these contests, which Dr. Jenner had an 

 opportunity of watching narrowly, and which was 

 continued for more than a day, the combatants 

 alternately appeared to have the advantage, each 

 having carried the other several times nearly to 

 the top of the nest, and then sunk down oppressed 

 with the weight of its burthen, till at last, one 



