42 BIRDS' NESTS 



Indeed, from a human point of view, we might 

 justly ascribe the habit of annexing some ready- 

 made nest, or that of relegating all responsibility of 

 the offspring to foster parents, to an exceptional 

 intelligence rather than to any want of it. Now, it 

 is a remarkable and interesting fact, and one going 

 far to prove the truth of the contention that nests 

 are purely and simply utilitarian structures, sub- 

 servient in every respect to the conditions under 

 which the young are produced, that we find nestless 

 species in so many of the great groups into which 

 birds are divided by systematists. Not only are 

 some of the most archaic avine forms devoid of any 

 nest-building propensity, but some of the species in 

 the more highly specialised groups are in an exactly 

 similar condition, whilst in not a few instances we 

 have nest-building as well as nestless species belong- 

 ing to the same family or even genus. In some 

 cases the general habits of the birds are almost the 

 same, yet some small divergence in the way the 

 young are produced determines whether there shall 

 be a nest or not. By common consent the Eatitse 

 (comprising the Rheas, Cassowaries, Emus, Kiwis and 

 Ostriches) is regarded as the most archaic order of 

 surviving birds, and yet none of the members of it 

 can be said to be nestless, as will be shown in the 

 following chapter. It is also a curious fact that in 

 some nest-building species individuals are occasionally 

 known to forego the habit and to omit making any 



