NATURAL HISTORY OF SELBORNE. 191 



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 extraordinary, 

 tney begin to retire still earlier in the most southerly parts of 

 Andalusia, where they can be in no ways influenced by any defect 

 of heat ; or, as one might suppose, failure of food. Are they 

 regulated in their motions with us by a defect 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 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 much infested with those pests to 

 the genus called hippoboscce hirimdinis ; 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 can 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 where 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 Gibraltar, 

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

 anticos " all its four toes forward ; besides, the least toe, which 

 should be the back toe, consists of one bone alone, and the other 

 three only of two apiece, a construction most rare and peculiar, 



