Of the three Humming-birds which visit the vicinity of Buenos Ayres in the summer months, Mr. Durnford tells us this is the rarest. It is occasionally seen in the riverain wood, and like the other two (_Hylocharis sapphirina_ and _Chlorostilbon splendidus_) may generally be found hovering over the flowers of the Ceiba-tree--a species of _Erythrina_. Further to the north this species would seem to be more abundant. Dr. Burmeister met with it near Tucuman and Paraná, and at one time described the young birds obtained in the latter locality as of a distinct species (_Campylopterus inornatus_), an error which he subsequently corrected (_cf._ P. Z. S. 1864, p. 466). White procured it in the city of Catamarca in August 1880. Mr. Barrows has published the following interesting account of his observations on this species in Entrerios (Auk, 1882, p. 21):-- "Early in September, at Concepcion, when the orange-trees are just whitening with blossoms, these magnificent Humming-birds arrive from the north, and may occasionally be seen about the orange-trees in any garden, as well as about blossoming trees elsewhere. The males seemed for some reason to be much less abundant than the females, hardly more than a dozen being seen in an entire season. They probably nest in November and December, and leave for the north again in February or March. A nearly finished nest, found November 17, was very similar to that of our own Ruby-throat (_Trochilus colubris_) but larger, and was built in the compound fork of a large limb at a height of over 25 feet from the ground. It was deserted soon after, perhaps as a result of my examination. Ten days later another nest was found saddled on the topmost horizontal limb of a dead and moss-grown stub; only about seven feet from the ground, and exposed to the full force of the sun. This nest contained two eggs nearly ready to hatch. Both nests were beautifully covered with lichens, and the last was lined with the finest of vegetable down. The female made several angry rushes at me before the nest was touched, but as soon as she saw that it was discovered became so shy that it was difficult to secure her. The male was not seen at all. I once saw a bird of this species attack and put to rout a wild dove which passed near it while feeding, and though the dove made every effort to escape, the Hummer not only kept up with it easily, but darted above and below it as well, and finally both went out of sight in the distance together." 236. LEUCIPPUS CHIONOGASTER (Tsch.). (WHITE-BREASTED HUMMING-BIRD.) +Leucippus chionogaster+, _Scl. et Salv. Nomencl._ p. 91; _White, P. Z. S._ 1882, p. 616 (Catamarca); _Elliot, Syn. Troch._ p. 199; _Gould, Mon. Troch._ v. pl. 290.