A. Basal phalanx of anterior toes abbreviated; that of median toe decidedly shorter than the basal of inner, or the two basal of outer, and adherent for its whole length on both sides to the lateral (i. e. not free at all). Lateral plates of tarsus undivided, except at extreme lower end.
Vireonidæ. Gonys more than half the length of lower jaw (from tip to angle of mouth), usually longer than width of mouth, which is narrow. Bill conical, much compressed, decurved at end and notched, but scarcely toothed. Frontal feathers bristly and erect, or bent but slightly forward. Nostrils overhung by membrane. Tarsus longer than middle toe and claw. Lateral toes generally unequal; outer claw reaching half-way along middle claw.
B. Basal phalanx of middle toe about as long as the basal of inner, or the two basal of outer; free externally, at least for about one third its length, internally for about one half. Lateral plates of tarsus with decided tendency to subdivision (except in Myiadestinæ).
Ampelidæ. Gonys decidedly less than half the length of lower jaw, or than width of mouth, which is very broad and deeply cleft. Bill triangular, much depressed, decurved at end and notched, with moderate though decided tooth. Frontal feathers rather soft, scarcely bristly or erect. Nostrils overhung by membrane. Tarsus equal to or shorter than middle toe and claw. Lateral toes nearly equal; outer claw reaching only to base of middle claw.
Laniidæ. Gonys about half the length of lower jaw; about equal to width of mouth. Bill very powerful and raptorial, much compressed, with a strongly marked hook, notch, and tooth at end. Frontal feathers very bristly, and directed forwards, so as to conceal nostrils and base of bill. Nostrils with bony walls, except behind. Tarsus longer than middle toe and claw, sometimes much scutellate on sides. Lateral claws nearly equal; outer claw reaching a little beyond base of middle claw.
Family VIREONIDÆ.—The Vireos.
The essential features of this family appear to consist in the combination of the dentirostral bill, notched in both mandibles; the ten primaries (except Vireosylvia), of which the outer is usually from one fourth to one half the second; the rather short, nearly even tail, with narrow feathers, and the great amount of adhesion of the anterior toes,—the whole basal joint of the middle being generally united on both sides to the adjacent joints, and decidedly shorter than the basal of inner or two basal of outer. The outer lateral toe is generally appreciably longer than the inner, reaching considerably beyond the base of the middle claw. The tarsi are always distinctly scutellate anteriorly. The young are never spotted, or streaked as in the Thrushes; nor, indeed, do the adults exhibit such markings.
The Vireonidæ are peculiar to the New World, and are widely distributed, although but one genus belongs to the United States.
Genus VIREO, Vieill.