34 BIRDS OF LA,PLATA 
COMMON SWALLOW 
Tachycineta leucorrhoa 
Above glossy dark green; rump white; quills black, washed with 
green; tail black with greenish gloss; base of forehead, cheeks, and 
whole under surface white; flanks and sides washed with smoky 
brown; length 5.5 inches. 
Tus is the most abundant and best known of our 
Swallows; a pretty bird in its glossy coat of deep 
green, and rump and under surface snowy white ; 
exceedingly restless in its disposition, quick and 
graceful in its motions; social, quarrelsome, gar- 
rulous, with a not unmusical song, beginning with 
long, soft, tremulous notes, followed by others 
shorter and more hurried, and sinking to a murmur. 
They are the last of all our migrants to leave us in 
autumn, and invariably reappear in small numbers 
about the houses on every warm day in winter. 
Probably many individuals in Buenos Ayres remain 
through the winter in sheltered situations, to scatter 
over the surrounding country whenever there comes 
a warm bright day. I once saw three together, 
skimming over the plains, on one of the coldest 
days I ever experienced on the pampas, the ther- 
mometer having stood at 29 deg. Fahrenheit that 
morning. 
Further south their migration is more strict ; and 
on the Rio Negro, in Patagonia, from March to 
