224 NATURAL HISTORY 



LETTER VIII. 



TO THE SAME. 

 DEAR SIR, SELBORNE, Dec. 20, 1770. 



THE birds that I took for Aberdavines were reed spar- 

 rows (Passeres torquati). 



There are, doubtless, many home internal migrations 

 within this kingdom that want to be better understood ; 

 witness those vast flocks of hen chaffinches that appear 

 with us in the winter without hardly any cocks among 

 them. Now, was there a due proportion of each sex, 

 it should seein 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 chaffinches (Frin- 

 gillce ccelebes), 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 separately, except at 

 the season when commerce is necessary for the conti- 

 nuance of the breed. For this matter of the chaffinches 

 see Fauna Suecica, p. 85, and Systema Naturae, p. 318. 

 I see every winter vast flights of hen chaffinches, but 

 none of cocks 1 . 



1 Amongst our vernal birds of passage, the cock birds generally arrive 

 about a fortnight before the hens, a circumstance well known to the bird- 

 catchers, who are certain that all which are caught out of the first flight 

 will prove males. The cock nightingales generally appear in the neigh- 

 bourhood of London on the 12th of April. They are sometimes taken a 

 few days earlier, but that is the day upon which those who make a trade 

 of catching them depend upon their arrival. 



It is very difficult to understand the reason of this precession of the 

 males. It has been supposed by some writers, that the females were 

 delayed by the care of a young brood; but it seems to me nearly certain 



