ON THE HEPATIC PLUMAGE OF THE CUCltOO. 325 



first two I have met with in the red dress, although I have 

 occasionally had examples with a feather here and there which 

 had not changed colour, — may be accounted for by the fact that 

 the change of colour in the feathers takes place, as a rule, before 

 the birds come to us in spring, and this will also explain their 

 comparative abundance on the Continent. 



In a normally healthy bird the change of colour would take 

 place rapidly. The specimens in the red condition of plumage 

 which we get in this country are simply examples of retarded 

 development. The cause of this failure on the part of the bird 

 to change the colour of its feathers at the proper time is known 

 to me, but for the present I reserve information on this point. 



It must be remembered that all red Cuckoos met with either 

 in England or abroad have been in the months of April or May. 

 We have no record of one found in June. What, then, becomes 

 of the hepatic Cuckoos after April or May ? The only answer, 

 I think, to this question is the theory I have above suggested. 



I do not think that Mr. Seebohm is right in asserting that 

 "the female Cuckoos just entering their second year do not 

 breed." From the examination of the ovaries in my two birds, 

 I should unhesitatingly say that they were breeding females. 

 And I cannot refrain from directing attention to the singular fact 

 that all the red Cuckoos whose sex has been ascertained have 

 proved to be females, with the exception of those mentioned by 

 Temminck. 



Mr. Harting states that the female examined by him showed 

 no marked development of the ovaries. If the bird was shot 

 early in April, no marked development could be expected in a 

 young bird ; but every week — nay, every day — would add to the 

 development of these organs at the breeding period. 



To briefly summarise, then, it seems to me that (1) Cuculus 

 canorus in the red or hepatic phase of plumage is the young bird 

 of the ensuing spring ; (2) that it does not moult until it is over 

 twelve months old ; and (3) that it is a gradual change of colour 

 in the feather which transforms it from the reddish nestling 

 stage to that of the adult grey bird. 





