NATURAL HISTORY OF SELBORNE. : < 2 7 



LETTER XXXIX. 



SELBORNE, May lyA, 1778. 



DEAR SIR, Among the many singularities attending those 

 amusing birds the swifts, I am now confirmed in the opinion that 

 we have 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 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 reoccupy their ancient haunts ? 



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

 have always supposed that that sudden ) averse of affection, that 

 strange avricrropyrj, 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 pro- 

 vision 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. 



IS 



