246 The Natural History of Selborne 



be gathered ; first, that many insects abide high in the air, even in 

 rain ; and next, that the feathers of these birds must be well preened 

 to resist so much wet. Windy, and particularly windy weather with 

 heavy showers, they dislike ; and on such days withdraw, and are 

 scarce ever seen. 



There is a circumstance respecting the colour of swifts, which 

 seems not to be unworthy of our attention. When they arrive in 

 the spring, they are all over of a glossy, dark soot colour, except 

 their chins, which are white ; but, by being all day long in the sun 

 and air, they become quite weather-beaten and bleached before they 

 depart, and yet they return glossy again in the spring. Now, if they 

 pursue the sun into lower latitudes, as some suppose, in order to 

 enjoy a perpetual summer, why do they not return bleached ? Do 

 they not rather perhaps retire to rest for a season, and at that juncture 

 moult and change their feathers, since all other birds are known to 

 moult soon after the season of breeding ? 



Swifts are very anomalous in many particulars, dissenting from all 

 their congeners not only in the number of their young, but in breed- 

 ing but once in a summer ; whereas all the other British hirundines 

 breed invariably twice. 1 It is past all doubt that swifts can breed but 

 once, since they withdraw in a short time after the flight of their 

 young, and some time before their congeners bring out their second 

 broods. We may here remark that, as swifts breed but once in a 

 summer, and only two at a time, and the other hirundines twice, the 

 latter, who lay from four to six eggs, increase at an average five times 

 as fast as the former. 



But in nothing are swifts more singular than in their early retreat. 

 They retire, as to the main body of them, by the tenth of August, 

 and sometimes a few days sooner ; and every straggler invariably 

 withdraws by the 2Oth, while their congeners, all of them, stay till 

 the beginning of October ; many of them all through that month 

 and some occasionally to the beginning of November. This early 

 retreat is mysterious and wonderful, since that time is often the 

 sweetest season in the year. But what is more extraordinary, they 

 begin to retire still earlier in the most southerly parts of Andalusia, 



1 See note on p. 243. ED. 



