132 
NATURAL HISTORY OF SELBORNE. 
themselves in flight, they raise their wings, and make them meet over 
their backs. 
At some certain times in the summer I had remarked that swifts 
were hawking very low for hours together over pools and streams ; and 
could not help inquiring into the object of their pursuit that induced 
them to descend so much below their usual range. After soihe 
trouble, I found that they were taking 'phryganece, ephemerce, and 
Ubellulce (cadew-flies, may -flies, and dragon-flies), that were just emerged 
out of their aurelia state. I then no longer wondered that they should 
be so willing to stoop for a prey that afibrded them such plentiful and 
succulent nourishment. 
They bring out their young about the middle or latter end of July ; 
but as these never become perchers, nor, that ever I could discern, are 
fed on the wing by their dams, the coming forth of the young is not so 
notorious as in the other species. 
On the 30th of last June, I untiled the eaves of a house where many 
pairs build, and found in each nest only two squab, naked puUi; on the 
8th of July I repeated the same inquiry, and found that they had made 
very little progress towards a fledged state, but were still naked and 
helpless. From whence we may conclude that birds whose way of life 
keeps them perpetually on the wing would not be able to quit their 
nest till the end of the month. Swallows and martins, that have 
numerous families, are continually feeding them every two or three 
minutes ; while 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 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 1 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 1 
Swifts are very anomalous in many particulars, dissenting from all 
their congeners not only in the number of their 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 congejiers bring out their second broods. 
