Myiarchus. Tarsus equal to the middle toe, which is decidedly longer than the hinder one. Tail even or rounded. Throat pale ash, rest of lower parts yellow generally, the primaries edged with rufous, and inner webs of tail-feathers with more or less of the same color. Nest in a cavity of a tree, of loose material; eggs whitish, with intricate tangled lines and streaks of dark brown, the general effect salmon-color.
Sayornis. Tarsus rather longer than the middle toe, which is scarcely longer than the hind toe. Tail slightly forked. Bill very narrow. No light orbital ring, nor distinct bands on wings; both mandibles black. Nest attached to rocks or parts of buildings, very compact and bulky, containing much mud in its composition; eggs pure white, immaculate, or with very minute sparse dots near larger end.
2. Tail decidedly shorter than the wings, which reach beyond its middle. Tarsus shorter than the middle toe.
Contopus. Hind toe much longer than the lateral. Tail considerably forked. Wings long, pointed; much longer than the tail, reaching beyond the middle of the latter; first quill about equal to the fourth. Bill broad. Color olive-gray, and white, sometimes with a yellowish tinge beneath. Lower mandible pale-colored. Nest saucer-shaped, compact, and very small, saddled very securely upon a thick branch; eggs cream-colored, with a zone of lilac and rich brown blotches round the larger end.
3. Tail shorter than the wings, as in the last. Tarsus considerably longer than the middle toe; hind toe much longer than lateral. Tail nearly even, sometimes slightly rounded, but little shorter than the wings; first primary much shorter than the fourth.
Empidonax. Head moderately crested; tail about even. Bristles of bill reaching about half-way to tip. Legs stout. A conspicuous light orbital ring, and distinct bands on the wing. More or less tinged with sulphur-yellow on lower parts. Nest variously constructed, deeply cup-shaped, compact or loose, entirely of either grassy or fibrous and downy material, and fixed to slender twigs or lodged in a crotch between thick branches; eggs white, immaculate, or with blotches of brown round larger end.
Mitrephorus. Head decidedly crested. Tail forked. Bristles of bill reaching nearly to tip. Legs very weak and slender. Beneath more or less tinged with fulvous or ochraceous.
Pyrocephalus. Head with a full crest. Tarsus but little longer than the middle toe; hind toe not longer than the lateral. Tail broad, even; first quill shorter than the fifth. Beneath, with whole crown bright red (except in P. obscurus). Female very different, lacking the red, except posteriorly beneath, and with the breast obsoletely streaked.
Genus MILVULUS, Swainson.
Milvulus, Swainson, Zoöl. Jour. III, 1827, 165.