Wizard Cuckoos 61 



It seems probable that there are separate races or 

 clans of hen cuckoos, each dependent on a separate 

 species of foster-parent. It would seem not un- 

 natural for the cuckoo to frequent the company 

 of the kind of bird by which she was brought up, 

 rather than that of other species with which she 

 has had no connexion. The partial assimilation 

 of the cuckoo's egg to those of its hosts' would 

 follow, on the principle of protective mimicry, from 

 the association of each clan with foster-parents of 

 a certain species. Then, however, the question 

 naturally presents itself why, given these stable 

 hereditary habits, the likeness of cuckoos' eggs to 

 those of their host is not more thorough. Appar- 

 ently the answer is provided by the fact that cuc- 

 koos neither pair, like the great majority of birds, 

 nor practise polygamy, like the pheasant and other 

 related species, but are polyandrous, if not actually 

 promiscuous. While the hens are respectively 

 attached to definite species, the cocks may have no 

 such ties. And since many different cocks mate 

 with a single hen, cross-currents of blood must thus 

 perpetually be introduced from other clans to con- 

 fuse the fixed hereditary strain of the hen. But the 

 influence of these cross-strains on the type of egg 

 is partly counteracted by their mutual opposition, 

 so that the hen cuckoos of each clan continue to 

 lay eggs imperfectly resembling those of their foster 

 species, though the resemblance is very slow in 

 becoming complete. 



The extreme smallness of the cuckoo's egg in 

 proportion to the size of the bird seems plainly 



