This species, distinguished from the Purple Martin by its white underparts, ranges from Mexico to Buenos Ayres, the extreme limit of its range being about 250 miles south of that city. It was well called _Golondrina domestica_ by Azara, being preeminently domestic in its habits. It never breeds in banks as the Purple Martin often does, or in the domed nests of other birds in trees, a situation always resorted to by the Tree-Martin, and occasionally by the Common Swallow; but is so accustomed to the companionship 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 apparently 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 several agreeably modulated notes, and in that thick rolling intonation peculiar to our Swallows. This song does not sound loud when near, yet it can be distinctly heard when the bird appears but a speck in the distance. I may here remark that, with the exception of the _Petrochelidon pyrrhonota_, which possesses a sharp squeaky voice, like the Swallows of Europe, all our Hirundines have soft voices: their usual twittering when they are circling about resembles somewhat the chirping of the English House-Sparrow in tone, but besides these notes they possess a song more pleasing to the ear. Before leaving in February these birds congregate in parties of from twenty to four or five hundred, usually on the broad leafy top of an old ombú tree. 27. PROGNE TAPERA (Linn.). (TREE-MARTIN.) +Progne tapera+, _Scl. P. Z. S._ 1872, p. 606 (Buenos Ayres); _Scl. et Salv. Nomencl._ p. 14; _Durnford, Ibis_, 1877, p. 168 (Buenos Ayres); _White, P. Z. S._ 1882, p. 595 (Catamarca); _Barrows, Bull. Nutt. Orn. Cl._ viii. p. 89 (Concepcion); _Sharpe, Cat. B._ x. p. 180. +Cotyle tapera+, _Burm. La-Plata Reise_, ii. p. 477. _Description._--Entire upper parts dull brown; tail-feathers blackish brown; throat ashy white; fore neck and chest ashy brown in the centre and dark brown on the sides, as are also the flanks; abdomen white; bill and feet horn-colour: total length 7 inches, wing 5·5, tail 2·6. _Female_ similar. _Hab._ Brazil, Paraguay, Argentina.