182 



THE NATURAL HISTORY 



[LETT. 



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, 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 searches, but almost eludes our guesses ! 



These hirundines never perch on trees or roofs, and so never 

 congregate with their congeners. They are fearless while haunt- 

 ing their nesting-places, and are not to be scared by a gnu ; and 

 are often beaten down with poles and cudgels as they stoop to 

 go under the eaves. Swifts are much infested with those pests 

 to the genus called Mppoboscce (Anaperce hirundinis, Leach), and 

 often wriggle and scratch themselves, in their flight, to get rid of 

 that clinging annoyance. 



Swifts are no songsters, and have only one harsh screaming 

 note ; yet there are ears to which it is not displeasing, from an 

 agreeable association of ideas, since that note never occurs 

 but in the most lovely summer weather. 



They never settle on the ground but through accident ; and 

 when down can hardly rise, on account of the shortness of their 

 legs and the length of their wings : neither can they walk, but 

 only crawl ; but they have a strong grasp with their feet, by 

 which they cling to walls. Their bodies being flat, they can 

 enter a very narrow crevice ; and when they cannot pass on their 

 bellies they will turn up edgewise. 



The particular formation of the foot discriminates the swift 

 from all the British hirundines; and indeed from all other known 

 birds, the Hirundo melba, or great white-bellied swift of Gibral- 

 tar, excepted ; for it is so disposed as to carry " omnes quatuor 

 digitos auticos" "all its four toes forward;" besides, the least 

 toe, which should be the back one, consists of one bone only, and 

 the other three of only two apiece : a construction most rare 

 and peculiar, but nicely adapted to the purposes in which their 

 feet are employed. This, and some peculiarities attending 

 the nostrils and under mandible, have induced a discerning 



