Vol.xlii.] 104 



7. How many, if any, of thie fosterer's eggs do Cuckoos take? 

 There is now am[)le evidence that the Cuckoo invariably 



takes one egg of the foster-parent in exchange for her own, 

 but when there is only one of the former I think she 

 generally leaves it. I have had at least a dozen instances 

 within my own knowledge of this occurring, and it is pro- 

 bably the rule and may sometimes extend to instances in 

 which there are only two fosterer's eggs in the nest when 

 the Cuckoo deposits her own. Mr. Scholey's remarks as to 

 this bird's habits in this respect are worth noting, for he 

 records the fact that time after time he has found two eggs 

 taken from a Reed- Warbler's nest in exchange for the one 

 of the Cuckoo's placed therein. In a letter to me he writes 

 that ho finds that when the foster-parent is a small bird the 

 Cuckoo takes two eggs, but in the larger birds, such as 

 Buntings, Accentors, etc., they take but one. 



8. What does the Cuckoo do with the stolen egg? 



The strong probability is that she eats it. No one has 

 found any remains of a stolen egg, unless the Cuckoo has 

 been suddenly startled with it in her possession. 



The above are a few only of the questions often asked, but 

 to me the most absorbing interest lies in the question — 



To what extent is adaptation being evolved in Cuckoos' eggs ? 



I have already written so much about this that my only 

 excuse for writing more is that probably no one here has 

 ever read my previous effusions. My theory is that amongst 

 Cuckoos we have various forms of birds which differ greatly 

 in the stage of evolution they have themselves reached. In 

 some genera, such as Clamator, we have species extending as 

 more or less resident birds over much of Europe, Asia, and 

 Africa which appear to be amongst the oldest forms, and 

 which have been parasitic for sufficient thousands — or it may 

 be millions — of o;enerations to have had evolved for them an 

 egg so suitable to their purposes that any other kind of egg 

 is unnecessary and abnormal. On the other hand, in the 

 genus Cuculus we find various degrees of evolution. Thus 

 the little Himalayan Cuckoo has now two very distinct types 



