342 COLYMBID.E. 



colour during winter, apparently confirming tlic opinion that 

 having once acquired a dark-coloured throat they do not 

 afterwards lose it at any season. M. Temminck, in the 

 4th part of his Manual, states it as now ascertained that the 

 Divers have a double moult in the year ; and Mr. Hey- 

 sham's specimen, as well as others, have been found to be in 

 moult in the spring. This is certainly in favour of a tem- 

 porary assumption of colour. Mr. Selby mentions that, of 

 the numbers which visit our shores in winter, adult specimens 

 might perhaps be estimated at not more than one in fifty ; 

 this seems a very large proportion of young birds, when we 

 consider that these Divers breed but once in a summer, and 

 seldom bring up more than two young birds ; sometimes only 

 one. Mr. Proctor saw flocks of Divers when at Iceland, in 

 the middle of summer, but not one of them had a white 

 throat, nor can I find any record of the capture of Divers 

 with a white throat in summer, except very late in that 

 season in Norway, and these were two small and young birds 

 of the year, only two or three months old. The few Divers 

 obtained with dark-coloured throats in winter, compared to 

 the number of those taken having white throats, seem to 

 make the former rather the exception than the rule, and I 

 have known a specimen of our common Tern, killed in 

 December, with a black head, thus, perhaps from some 

 morbid cause, carrying the strongest mark of its breeding- 

 plumage through the winter. 



