l6o THE WORLD'S BIRDS. 



grade, not standing upon the toes. They dimb 

 and chng well, but only a few perch on trees in the 

 ordinary way. They are seldom seen otherwise 

 than on the wing. 



Flight. — Swift and easy, some being said to be the 

 swiftest of all birds. Sometimes they cannot rise 

 off the ground, but not by any means always. 



Note. — A twitter or scream. They never sing as some 

 swallows do. 



Disposition and Habits. — Lively and sociable ; they 

 are also courageous, often turning sparrows and 

 swallows out of their nests. 



Economic Qualities. — Except when they displace 

 swallows, they are highly beneficial by reason 

 of their feeding habits. One species [Collocalia 

 francica)^ which builds entirely with its sticky 

 saliva, produces the valuable " edible birds' - 

 nests " of Eastern commerce. 



Captivity. — They have never been kept in this state 

 for any length of time. 



Distribution and Important Species. — ^There are 

 about a hundred species in this family, which 

 is found all round the world, chiefly in warm, 

 but also in temperate climates ; those frequenting 

 the latter migrate south in winter ; there are none 

 in New Zealand. The familiar sooty-brown British 

 species {Cypselus apus) extends over a large part 

 of the Old World ; but the common Swift of tropical 

 Africa and India is Cypselus affinis, smaller and 

 blacker than the British species, with a white 

 patch on the back. The Great Alpine Swift 

 (Cypselus melha), light brown above, white below, 

 is also a widely-distributed European species, but 

 only a straggler in England. The common Swift 

 of North America is the Chimney Swift (Chaetura 

 pelasgia), black, with a spiny tail, building a nest 

 of glued twigs in chimneys. 



