ORDER PASSERES* 91 



SO far to the south as the other species above named. Once 

 arrived in this country, they are not observed to desert it 

 again until the usual period of their return ; but in the south 

 of Europe, according to Spallanzani, they will retire to the 

 south even after their arrival, in the event of a prevalence of 

 sharp and cold winds, and return again in settled fine weather. 

 The experiments alluded to in the former part of these obser- 

 vations, on the genus, evince that some degrees below freezing 

 will not destroy these birds, even when left altogether 

 exposed. 



The swallow builds in general in the inside of chimnies, in 

 which no fires are kept, and sometimes in other covered 

 shelters about buildings. The female is said to have but 

 two broods here: the first, about five, is probably more 

 numerous than the second : the eggs are white, Avith reddish 

 spots, while those of the marten are simply white. The 

 experiment of marking a pair of these birds, by tying a 

 silken thread to the leg or otherwise, has evinced, by the 

 return of the same individuals to the same spot, in the 

 following season, that they are monogamous. The parental 

 tie appears to be equally strong as in the marten. 



In their habits, instincts, persons, migration, &c. the 

 swallow, the marten, and the swift are greatly assimilated. 

 Their physical specific differences are mentioned in the text ; 

 and their instincts, equally disposed in favour of human habi- 

 tations, diff^er only in the preference of one for the chimney, 

 and of the other for the window ; a difference which, however 

 unimportant, is nevertheless curious for its undeviating 

 nature in both. 



The River SioaUoto (H. riparia. lAx\.) does not arrive 

 in this country until a few days after the swallow and marten, 

 and it is thought to return to the south about the same time 

 before them. They nestle in holes made principally in 

 sand-banks which are two or three feet in length horizontally. 

 The eggs, from four to six, are white. They may be seen 



