468 THE CUCKOO 



aware, is the only case in which he is said to have given her 

 assistance. 1 



It may here be noted that the abnormally small size of the cuckoo's 

 egg makes it easy to hold it in the beak, possibly also in the pouch 

 under the tongue. How small it is compared with the size of the bird 

 may be judged from the fact that it is not much bigger than that of a 

 hedge-sparrow, though this species is considerably less than half the 

 size of the cuckoo. The unusual hardness of the shell is another 

 advantage, especially when the bird happens to be pushing its head 

 and neck in through the narrow entrance of a closed nest. 



In the case of closed nests it is clearly impossible for the cuckoo 

 to introduce its egg other than by putting it in with its beak. But this 

 necessity would not apply in the case of open nests strong enough to 

 support the bird if it sat upon them. That it occasionally does so 

 is certain. Naumann had the good fortune to see one lay its egg 

 directly in the nest of a reed-warbler, and he noted that it maintained 

 its position with the aid of wings and tail, which were pressed against 

 the reeds surrounding the nest. 2 Another was seen to sit on a pied- 

 wagtail's nest, and there lay its egg. 3 In a third instance, the bird 

 appears to have made an attempt to lay in the nest of a yellow- 

 hammer, but without success. The nest, after the cuckoo had left it, 

 was found with the sides pressed apart, and the lining outside, pre- 

 sumably caught in the cuckoo's claws and thus pulled out. The 

 cuckoo's egg also lay outside. 4 Though it is clear from what pre- 

 cedes that the cuckoo has two methods of introducing its egg into 

 the nests of its victims, to what extent each is used is a question 

 to which no satisfactory answer can yet be given. 



When putting its egg into a nest, the cuckoo is in the habit of 

 removing one or more of those of the owner. These are frequently 

 found on the ground beneath a nest which contains a cuckoo's egg. 

 An instance is given above (p. 466). The bird has also been caught 



1 Naumann, Vogel Mitteleuropas, iv. 404; J. A. Link, op. cit., p. 135. 



* Vogel Mitteleuropas, iv. 406. 



3 Field, 1897, Ixxxix. 027. 4 J. A. Link, op. cit., 134. 



