A YOUNG CUCKOO 65 



Selection, based as it is upon the assumption that 

 birds discriminate in favour of those eggs most 

 nearly approximating to their own ? If ever such 

 approximation was wanted but lacking, and if ever 

 such discrimination was practised, it was surely 

 when the foisting of the Cuckoo's egg upon other 

 birds was first attempted. 



But need we go further than this problem of the 

 Cuckoo's egg to find that birds do not discriminate 

 in such a manner. The vast difference existing 

 between the eggs of the Cuckoo and those of one 

 of its most frequent dupes the Hedge-sparrow 

 is scarcely disposed of by Professor Newton's 

 " explanatory hypothesis," when he writes : " We 

 know that certain kinds of birds resent interference 

 with their nests much less than others, and among 

 them it may be asserted that the Hedge-sparrow 

 will patiently submit to various experiments. She 

 will brood with complacency the egg of a Redbreast 

 (Erithacus Rubecula), so unlike her own, and for 

 aught we know to the contrary, may even be colour- 

 blind. In the case of such a species there would be 

 no need of anything further to insure success the 

 terror of the nest-owner at seeing her home invaded 

 by a Hawk-like giant, and some of her treasures 

 tossed out, would be enough to stir her motherly 

 feelings so deeply that she would without misgiving, 

 if not with joy that something had been spared to 

 her, resume the duty of incubation as soon as the 

 danger was past. But with other species it may, 

 nay doubtless it is, different. Here, assimilation of 

 the introduced egg to those of the rightful owner 

 may be necessary, for there can hardly be a doubt 



