AVES. 317 



on account of their numbers and rapidity of flight, they have found a place 

 in the literature of all civilized people, ancient and modern. 



These birds exhibit the social instinct to an extent rarely observable. 

 Individuals of the same and sometimes of different species build their nests 

 close together, and the birds themselves are almost constantly seen in 

 flocks. They are very fond of frequenting the vicinity of the water, over 

 the surface of vi'hich they may be seen skimming for hours. In fair weather 

 they occasionally ascend to a great height in the atmosphere, but are 

 usually occupied in the lower strata. 



Although the species are small birds, ihe swallows are sought after as 

 articles of food in some countries, to the neglect of those laws of common 

 sense which would protect birds so useful in the destruction of hosts of 

 diurnal insects, which are their only food. They are, however, generally 

 protected by public sentiment and by special enactment in some of the 

 states of North America. In Europe, also, they are generally much 

 regarded ; but in one country, Tuscany, they are placed directly beyond 

 protection, being classed amongst those vermin which it is always lawful 

 to destroy. 



The swallows are eminently migratory, and show great regularity in then- 

 periods of departure and return. In the course of several years, some 

 species will hardly vary more than a day or two in arriving at their nesting 

 places from the south. Thus the Chimney bird {Acantkylis ■pelasgia) 

 arrives in Pennsylvania from the 17th to the 20th of April ; the Martin 

 [Frogne purpurea) from the 28th of March to the 5th of April ; the Barn 

 Swallow [Hirundo rufa) from the 9th to the 13th of April. These dates 

 are of course subject to some variation from the different states of the 

 weather, as, for instance, in case of a few days of severe cold or of a snow 

 storm ; but the mean results of the observations of several seasons show 

 surprising uniformity. 



Sub-fam. 1. HirundinincB, or House Swallows. Head rather broad and 

 depressed ; bill short and more or less flattened and triangular, with the 

 sides rather abruptly compressed towards the point, gape very wide. Wings 

 long and pointed, first quill longest ; tail usually forked ; tarsi short ; toes 

 rather long and slender. Size small. 



The true swallows are more beautiful in their plumage and more graceful 

 in their movements than any other birds of this family. Several species 

 occur in North America, the largest and most conspicuous of which is the 

 Purple Martin, or House Martin, as it is frequently called from its sociable 

 and familiar disposition (Progne purpurea). It is spread abundantly through- 

 out the United States in the summer, spending the winter in South America. 

 It is an universal favorite with the American population, and comes con- 

 fidently to take possession of the little boxes or other habitations every- 

 where provided for its accommodation, as a sort of compensation for which 

 it drives away all the hawks disposed to visit the establishment, destroys 

 numerous insects injurious to vegetation, and, it may be added, if its box 

 is near the house of its protector, is as good as an alarm clock to awaken 

 I jm precisely at daybreak, by its incessant though not unpleasant chattering. 



521 



