NOTES ON MIGRANTS AND MOULT 33 



spring, body and tail or part ; others do not appear to 

 do so. 



My experience of Whitethroats seems to be much the 

 same as that of Miss Baxter and Miss Rintoul : thus, of 

 twenty-three spring Common Whitethroats, three specimens 

 show active moult ; one on 6th May has a few chin feathers in 

 quill, and another (same date) has odd body feathers in quill 

 and many old worn feathers, another (29th April) has the 

 central tail feathers not fully grown. Of the rest, some are in 

 fairly fresh plumage everywhere, some are very abraded 

 everywhere, but many show feathers of two ages, i.e., quite 

 fresh and quite abraded, but no active moult ; thus one on 

 7th May has part of the upper tail coverts, part of the body 

 plumage, and the central pair of tail feathers quite fresh, the 

 rest very worn, the wings are abraded but some of the inner 

 secondaries seem newer. That some Whitethroats of both 

 species moult in spring and others do not has long been 

 known to me, and the same explanation had often occurred 

 to me, viz., that only the birds of the previous year do a 

 complete moult in spring (body, wings and tail). Whether 

 this is so or not is a very difficult matter to prove, as 

 unfortunately (as I have before pointed out, Ibis, 191 1, 

 p. 401) there is a dearth of material of our summer visitors 

 obtained in their winter quarters during the season of 

 * expectc 1 moult, and until this want is made good many 

 problems cannot be satisfactorily solved ; however, as regards 

 the Common Whitethroat I think that this explanation does 

 not hold good for this reason : the first winter males are 

 distinguishable from the adult winter males by their much 

 browner heads and lesser coverts and usually less pure white 

 in the tail. Now I have several spring males obtained on 

 migration in May in England showing no active moult which 

 are retainitig 2invioulted and very ivorn the broivn head and 

 lesser coverts of the first winter plumage — individual feathers of 

 the tail, and possibly of the wing also, have been renewed, but 

 most are worn. Furthermore, the very fact that the spring 

 moult in this species is often variable and incomplete tends, 

 I think, to show that age is not a factor. I think one may 

 safely surmise that those birds which in April or May show 

 50 E 



