214 NATURAL HISTORY 



every year the same number of pairs invariably ; at least the 

 result of my inquiry has been exactly the same for a long 

 time past. The swallows and martins are so numerous, and 

 so widely distributed over the village, that it is hardly possible 

 to recount them ; while the swifts, though they do not all build 

 in the church, yet so frequently haunt it, and play and 

 rendezvous round it, that they are easily enumerated. The 

 number that I constantly find are eight pairs; about half of 

 which reside in the church, and the rest build in some of the 

 lowest and meanest thatched cottages. Now as these eight 

 pairs, allowance being made for accidents, breed yearly eight 

 pairs more, what becomes annually of this increase; and what 

 determines every spring which pairs shall visit us, and re- 

 occupy their ancient haunts ? 



Ever since I have attended to the subject of ornithology, I 

 have always supposed that that sudden reverse of affection, 

 that strange avrisropyri, which immediately succeeds in the 

 feathered kind to the most passionate fondness, is the occasion 

 of an equal dispersion of birds over the face of the earth. 

 Without this provision one favourite district would be crowded 

 with inhabitants, while others would be destitute and forsaken. 

 But the parent birds seem to maintain a jealous superiority, 

 and to oblige the young to seek for new abodes : and the 

 rivalry of the males, in many kinds, prevents their crowding 

 the one on the other. Whether the swallows and house- 

 martins return in the same exact number annually is not easy 

 to say, for reasons given above : but it is apparent, as I have 

 remarked before in my Monographies, that the numbers 

 returning bear no manner of proportion to the numbers 

 retiring. 



