Plumage of Cuckoos 167 



here, unless their feathers are reproduced much quicker 

 than is the case with most other birds. However improb- 

 able such a thing may appear upon the face of it, I am, 

 therefore, inclined to think that, occasionally at any rate, 

 young Cuckoos may revisit our shores in spring in the same 

 dress in which they left in the autumn (i.e. in their first 

 plumage) ; and that, being here and engaged in breeding, 

 they find it expedient to defer the moult of their flight 

 feathers so long, that when they leave us a second time 

 they are still actually wearing a considerable portion of 

 their first plumage ; or, in other words, they do not com- 

 plete a full moult until they are more than a year old, and 

 they help to continue their kind in the interval. It seems 

 curious that all the individuals of one family should not 

 behave in the same manner ; but similar cases of divergence 

 from rule are not unknown elsewhere, and it must not be 

 forgotten that some young Cuckoos are scarcely full-grown 

 when they leave us in August or September, while others 

 of their companions have already been on the wing several 

 weeks, and are by so much older. Some of these older 

 birds may, perhaps, complete their change to the adult blue 

 plumage before their return in spring, while younger indi- 

 viduals may not do so. Or, on the other hand, none of 

 the young may moult until almost the end of their first 

 year, and it may be only the more advanced of them that 

 come back to us to breed in May. I do not pretend to 

 know how far this may be so, or whether young birds in 

 red plumage are ever seen, say in Africa, during summer ; 

 but merely throw out the suggestion as a possible explana- 

 tion of why a few red Cuckoos are always found here in 

 summer. Perhaps, too, males may moult before they come 

 back, while females may not do so, and this may be par- 

 ticularly the case with young birds. 



One Cuckoo, a breeding female, examined on 25th June, 

 had nearly completed the assumption of her blue dress, 

 but not quite. Over the body a few red feathers still 

 remained : the tail and primary quills had all been renewed, 

 and were blue and practically full grown, but about half of 

 the secondaries were still red. The new secondaries were also 



