368 CYPSELlDyE. 



elates of their parents had departed (Mag. Nat. Hist, 

 ser. 2, i. p. 110). 



Year by year the Swift revisits its old haunts, generally 

 arriving in pairs, and, unless access to its accustomed lodg- 

 ings has heen made impossible, it will reoccupy them, as 

 proved nearly a century since by Jenner (Phil. Trans. 18*24, 

 p. 16), who determined the identity of some of the birds so 

 returning by marking them indelibly*. New buildings it 

 seldom affects, partly no doubt because, owing to their con- 

 dition, it cannot effect an entrance to them, and Gilbert 

 White, in his unsurpassed monograph of the species, has 

 noticed the fact of a particular locality being annually fre- 

 quented by exactly the same number of pairs of birds 

 throughout a long series of years. Almost every natural 

 function of the Swift sleep, oviposition and incubation 

 excepted seems to be performed in the air, and its evolu- 

 tions on the wing have been admirably described by Macgil- 

 livray in terms which need not be repeated here. A most 

 engaging sight it is to watch its movements aloft, but it is 

 no less interesting to behold some half-dozen birds racing, 

 as they often do, within a few feet of the ground through 

 the narrow lanes or up and down the most confined courts of 

 a small country town or village, uttering the while their 

 singular squealing note, which writers have tried to syllable 

 swee-ree. This cry has obtained for the bird in some parts 

 of England the name of " Screech-Owl "t, and its emission 

 has been thought by some observers to depend on the state 

 of the weather, which is no more true than that is indicative, 

 as Macgillivray held, of an abundance of prey. It seems to 

 be of the nature of a song |, and is probably peculiar to the 

 male, when impelled by the same feelings of love or jealousy 

 as actuate other birds. It is seldom heard far from the 

 breeding-place, though the Swift, as before stated, roams 



* One of the examples marked by him was recognized seven years afterwards. 

 So little is known of the age to which birds attain, that this piece of incontro- 

 vertible evidence is worth preserving. 



+ Another common name is "Deviling." 



t It must be remembered, however, that the Swift has no true song-muscles. 



