NATURAL HISTORY 



LETTER XXXIX. 



TO THE SAME. 

 DEAR SIR, SELBORNE, May 13, 1778. 



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 inva- 

 riably; 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 cot- 

 tages. Now, as these eight pairs, allowance being made 

 for accidents, breed yearly eight pairs more, what be- 

 comes annually of this increase; and, what determines 

 every spring which pairs shall visit us, and reoccupy 

 their ancient haunts 1 ? 



1 Mr. White observes also, in a former letter, that there must be a great 

 destruction of swallows somewhere ; because they do not return in the 

 same numbers that departed from hence. But this is the case with all 

 birds in a wild state, unless under particular circumstances; the numbers 

 are not greater each successive spring, however prolific the parents may 

 be, but the supply is fitted to the consumption. It may be readily con- 

 ceived, that large numbers of our birds of passage may be destroyed by 

 birds of prey in the interior of Africa, and it is more difficult to account 

 for the annual consumption of the small birds that remain the whole year 

 with us, where the hawks are much destroyed and few in number. Night- 

 ingales live nine or ten years in confinement, and there is no reason to 

 believe swallows to be more short-lived. Chaffinches and yellowhammers 

 have few enemies but the sparrow hawk ; and yet, supposing each pair to 

 raise but six young, which if they breed twice must be a low average, 



