(RED-BACKED ROCK-MARTIN.)
+Petrochelidon pyrrhonota+, _Scl. et Salv. Nomencl._ p. 14; _Durnford,
Ibis_, 1877, p. 169; _White, P. Z. S._ 1882, p. 595 (Buenos
Ayres); _Sharpe, Cat. B._ x. p. 193. +Cotyle pyrrhonota+, _Burm.
La-Plata Reise_, ii. p. 477 (Tucuman).
_Description._--Above glossy dark steel-blue; lower back and rump
cinnamon-rufous; the upper tail-coverts brown, with grey margins;
wings black; tail black, with greenish gloss; crown steel-blue;
forehead sandy buff; cheeks and sides of face chestnut, spreading
to the sides of the hind neck; chin chestnut; the lower throat
steel-blue; fore neck, chest, and sides of body and flanks light
ashy brown; centre of breast and abdomen white, tinged with brown;
under tail-coverts, also under wing-coverts and axillaries, ashy
brown: total length 5·3 inches, wing 4·35, tail 2·05. _Female_
similar.
_Hab._ South America.
This species does not breed in Buenos Ayres, and is only seen there in
spring, flying south or south-west, and again in much larger numbers on
its return journey in autumn. On the Rio Negro, in Patagonia, I did
not meet with it, and suppose its summer resort must be south of that
locality; and, judging from the immense numbers visible in some seasons,
I should think that they must, in their breeding-place in Patagonia,
occupy a very extensive area. They do not seem to be as regular in
their movements as other Swallows here; some years I have observed them
passing singly or in small parties during the entire hot season: usually
they begin to appear, flying north, in February; but in some years not
until after the middle of March. They are not seen passing with a rapid
flight in close flocks, but straggle about, hawking after flies: first
one bird passing, then two or three, and a minute or two later half a
dozen, and so on for a greater part of the day. So long as the weather
continues warm they journey in this leisurely manner; but I have known
them to continue passing till April, after all the summer migrants had
left us, and these late birds flew by with great speed in small close
flocks, directly north, as if their flight had been guided by the
magnetic needle.
While flying this species continually utters sharp twitterings and
grinding and squealing notes of various lengths.