NATURAL HISTORY OF SELBORNE. 179 
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 con- 
gregate 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 
WHITE-BELLIED SWIFT. 
the eaves. Swifts are much infested with those pests to the genus 
called hippobosce hirundinis, and often wriggle and scratch them 
selves 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 
