THE CUCKOO AND HIS KINDRED. 133 



a perceptible tendency among Cuckoos to use the 

 nest of certain species. Where the egg has been 

 obviously phiced in a wrong nest, either as regards 

 species or colour of the egg, it may be safely 

 assumed that the parent Cuckoo, in danger of 

 immediate dehvery, has been compelled to use tlie 

 first nest obtainable, or has been unsuccessful in 

 finding a nest of the species to which individually 

 it is most closely attached. The choice normally 

 is comparatively a narrow one, and confined to 

 such exclusively insectivorous species as the Mota- 

 ciLLiD.E, to the Sylviinan, the Redstarts, and the 

 Hedge Accentor. Many other species have been 

 known to be selected, even amongst the Frin- 

 GiLLiD.^, and more exceptionally a Crow, a Shrike, 

 a Grebe, or a Pigeon. It is a most significant fact, 

 that the eggs of the Great Spotted Cuckoo (an 

 equally parasitic species) are subject to remarkably 

 little variation, very closely resembling those of the 

 Common Magpie in appearance, and that the foster- 

 parents are generally Crows of some kind. The 

 eggs in this group are very uniform in colour, 

 hence we find a corresponding small variation in 

 the tint of those of the parasite Cuckoo which are 

 hatched amongst them. 



Another very curious instinct of the Cuckoo 



