26 BIRDS OF LA PLATA 
Swallow ; but is so accustomed to the companion- 
ship of man as to make its home in populous towns 
as well as in country houses. It arrives in Buenos 
Ayres about the middle of September, and appar- 
ently resorts to the same breeding-place every year. 
A hole under the eaves is usually selected, and the 
nest is roughly built of dry grass, hair, feathers, and 
other materials. When the entrance to its breeding- 
hole is too large, it partially closes it up with mud 
mixed with straw ; if there be two entrances it stops 
up one altogether. The bird does not often require 
to use mud in building; it is the only one of our 
Swallows that uses such a material at all. The eggs 
are white, long, pointed, and five in number. 
In the season of courtship this Martin is a noisy 
pugnacious bird, and always, when quitting its nest, 
utters an exceedingly loud startling cry several times 
repeated. It also has a song, uttered both when 
resting and on the wing, composed of nine or ten 
agreeably modulated notes, invariably repeated in 
the same order. It is a pleasing song with something 
of that peculiar human-like quality in the sound 
which is so engaging in our Barn Swallow. But it is 
a voice of much greater power and may be heard 
when the bird sings flying at so great a height as to 
be invisible. 
Before leaving in February these birds congregate 
in parties of from twenty to four or five hundred, 
their congregating place being usually on the broad 
leafy top of an old ombit tree. 
