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 which 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, the 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 their 
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 (Acanthylis pelasgia) 
arrives in Pennsylvania from the 17th to the 20th of April; the Martin 
(Progne 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. Hirundinine, or House Swallows. Wead 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 Jongest ; 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 
.im precisely at daybreak, by its incessant though not unpleasant chattering. 
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