376 



NATURAL HISTORY OF BIRDS. 



to have some difficulty in obtaining the fertilization of their ovaries. The extreme 

 voracity of the young bird is an additional reason why the care of the five nestlings 

 should be entrusted to as many pairs of birds. 



" In its choice of a foster-parent for its offspring, it exercises more discrimination 

 than might be supposed from the long lists which have been published of birds in 

 whose nests its eggs have been found. An insectivorous bird is generally chosen, and 

 preference is given to such as build open nests. Sometimes the cuckoo is unable to 

 find the nest of a suitable bird, and is obliged to deposit its egg in the nest of a 

 granivorous bird, such as the various species of finches, buntings, etc., and occasion- 



FIG. 179. Cuculus canorus, European cuckoo. 



ally cuckoos' eggs have been found in the nests of such totally unsuitable birds as 

 magpies, jays, shrikes, pigeons, and even the little grebe. The young cuckoo is 

 usually much larger than its foster-brothers or sisters, and monopolizes the attention 

 of the parents to the exclusion of the other inhabitants of the nest, who die or are 

 eventually expelled by the young cuckoo. It has been said, on what appears to be 

 incontestable evidence, that the young cuckoo, soon after it is hatched, ejects the 

 young or eggs from the nest by hoisting them on its back ; but one feels inclined to 

 class these narratives with the equally well-authenticated stories of ghosts and other 

 apparitions which abound. 



" The eggs of the cuckoo are subject to great variation of color, and they very 

 frequently resemble closely the eggs amongst which they have been placed, so much 



