174 NATURAL HISTORY OF SELBORNE. 



swifts, that have but two young to maintain, are much at their 

 leisure, and do not attend on their nests for hours together. 



Sometimes they pursue and strike at hawks that come in their 

 way ; but not with that vehemence and fury that swallows express 

 on the same occasion. They are out all day long in wet days, 

 feeding about, and disregarding still rain : from whence two 

 things may 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 parti- 

 cularly 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 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 then* young, 

 but in breeding but once in a summer ; whereas all the other 

 British hirundines breed invariably twice. 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 strag- 



* Swifts invariably moult during their absence ; and 1 am greatly inclined to suspect that the 

 young undergo no change whatever until the second autumn, as is the case with the whole falcon- 

 family, certain of the owls, and the bee-eater and king-fisher tribes, all of which require a long* 

 time to elaborate their first or nestling plumage, and many of which (1 believe all the falcon- 

 race) do not propagate till they are two years old. ED. 



