206 NATURAL HISTORY 



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 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 10th of August, and sometimes a few days sooner: 

 and every straggler invariably withdraws by the 20th, 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 extra- 

 ordinary, they begin to retire still earlier in the most 

 southerly parts of Andalusia, where they can be no ways 

 influenced by any defect of heat ; or, as one might suppose, 

 defect of food. Are they regulated in their motions with us 

 by a failure of food, or by a propensity to moulting, or by a 

 disposition to rest after so rapid a life, or by what ? This 

 is one of those incidents in natural history that not only 

 baffles our researches, but almost eludes our guesses ! 



These Hirundines never perch on trees or roofs, and so 

 never congregate with their congeners. They are fearless 

 while haunting their nesting places, and are not to be scared 

 with a gun, and are often beaten down with poles and 

 cudgels as they stoop to go under the eaves. Swifts are 



