242 FRIENDS WORTH KNOWING. 
Andean countries. On both continents its wanderings ex- 
tend to the extreme north, where, in Alaska, it is one of the 
commonest summer visitors. So this modest little bird, 
smallest of his kind, is entitled to our respect as a travel- 
ler at least; and, to compare the habits and appearance of 
the representatives in different portions of the globe of so 
widely distributed a species, becomes a most interesting 
study. 
Cotyle riparia, the bank-swallow, sand-martin, sand-swal- 
low, river-swallow, Phirondelle de rivage, or back-svala, is 
generally diffused over the northern hemisphere, though 
very unequally, avoiding those spots unfavorable to it. 
In this distribution it seems to have been somewhat influ- 
enced by man, though owing him no other favors than the 
incidental help of railroad-cuttings and sand -pits, which 
have increased the sites suitable for its nests, and thus ena- 
bled the species to spread inland. 
It is one of the earliest birds to arrive in the spring, ap- 
pearing in Old England during the last week in March, and 
in New England early in May—many passing on to the 
shores of the Arctic Ocean, where Richardson, at the mouth 
of the Mackenzie, and Dall, on the Yukon, found them 
breeding in immense numbers. In these high latitudes its 
summer is necessarily a brief one, and September finds 
