Tachycineta, Cab. Mus. Hein. 1850, 1851, 48. (Type, H. thalassina, Sw.)
Hirundo thalassina.
1895
Gen. Char. Nostrils lateral, overhung or bordered internally by incumbent membrane. Tarsi with the tibial joint covered by overhanging feathers, adherent a short distance along inner face, about equal to middle toe without claw. Lateral toes equal. Adhesion of basal joint of middle toe variable. Tail emarginate only, or slightly forked; fork not exceeding half an inch in depth. Color blue or green above, with or without metallic gloss; with or without white rump. Entirely white beneath. Nest usually in holes of trees or rocks; eggs pure white, unspotted.
Of this section there are two North American species, differing as follows, both being green above and white beneath:—
Species.
Plumage above soft and velvety without metallic gloss. Sides of head, space around eyes, and whole under parts, white; with the feathers all plumbeous at base. Female duller in plumage. Young with bases of throat-feathers gray to roots.
T. thalassina. Above velvety-green, with various shades and tinges of violet and purple.
Plumage above compact, and with rich green metallic gloss. Sides of head to line with eyes like its upper part. Beneath white; the feathers of chin and throat, and generally of crissum, white to base. A concealed spot in jugulum. Female duller. Young with bases of throat-feathers pure white to roots.
T. bicolor. Above metallic-green. Inside of wings and axillars ash-color.