194 SWIFTS. 



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 their 

 young, but in breeding but once in a summer ; whereas all 

 the other British Tiirundines 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 Jiirun- 

 dines 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 more 

 southerly parts of Andalusia, where they can be nowise 

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

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



* Mr. Yarrell says that the swift departs before its moult, and when it8 

 plumage is at the worst from wear and tear. Our summer visitors generally 

 complete their moult before they leave us, but not the Hirundinidae. 



