210 SWIFTS. 



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 some- 

 times a few days sooner ; and every straggler in- 

 variably withdraws by the 20th : while their con- 

 geners, all of them, stay till the beginning of Oc- 

 tober, 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 extraordinary, 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 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 

 much infested with those pests to the genus, 

 called hippoboscce hirundines, 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 



