LETTER XLI. 

 To THE Honourable Daines Barrington. 



The birds that 1 took for aberdavincs were reed- 

 sparrows {Passer es torqiiati). 



There are doubtless many home internal migra- 

 tions within this kingdom that want to be better un- 

 derstood ; witness those vast flocks of hen chaffinches 

 that appear with us in the winter with hardly any 

 cocks among them. Now, was there a due propor- 

 tion of each sex, it would seem very improbable that 

 any one district should produce such numbers of 

 these little birds ; and much more when only one half 

 of the species appears ; therefore we may conclude 

 that the Fringillos coelebes, for some good purposes, 

 have a peculiar migration of their own in which the 

 sexes part. Nor should it seem so wonderful that 

 the intercourse of sexes in this species of birds should 

 be interrupted in winter; since in many animals, and 

 particularly in bucks and does, the sexes herd sepa- 

 rately, except at the season when commerce is neces- 

 sary for the continuance of the breed. For this mat- 

 ter of the chaffinches, see '' Fauna Suecica," p. 85, and 

 '' Systema Naturse," p. 318. I see every winter vast 

 flights of hen chaffinches, but none of cocks. 



Your method of accounting for the periodical 



motions of the British singing birds, or birds of 



flight, is a very probable one ; since the matter of 



152 



