The Martin makes its own nest chiefly of large feathers, and lays four eggs, long, pointed, and pure white.
It will be remarked that in all its habits above mentioned this bird differs widely from the two preceding species. It also differs greatly from them in its manner of flight. The Purple Martins move with surprising grace and celerity, the wings extended to their utmost; they also love to sail in circles high up in the air, or about the summits of tall trees, and particularly during a high wind. At such times several individuals are usually seen together, and all seem striving to outvie each other in the beauty of their evolutions.
The Tree-Martin is never seen to soar about in circles; and though when hawking after flies and moths it sweeps the surface of the grass with amazing swiftness, at other times it has a flight strangely slow and of a fashion peculiar to itself: the long wings are depressed as much as those of a Wild Duck when dropping on to the water, and are constantly agitated with tremulous flutterings, short and rapid as those of a butterfly.
Neither is this bird gregarious like all its congeners, though occasionally an individual associates for a while with Swallows of another species; but this only when they are resting on fences or trees, for as soon as they take flight it leaves them. Once or twice, when for some mysterious cause the autumnal migration has been delayed long past its usual time, I have seen them unite in small flocks; but this is very rare. As a rule they have no meetings preparatory to migration, but skim about the fields and open plains in un-Swallow-like solitude, and suddenly disappear without having warned us of their intended departure.
[28.] PETROCHELIDON PYRRHONOTA (Vieill.).
(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.