The American Sylviidæ are in some respects very closely related to the Saxicolidæ, but may be distinguished by their much smaller size, more slender and depressed bill, more strongly bristled rictus, etc.; on which account they are more strictly “fly-catchers,” taking their prey in great part on the wing.
Of the three families, the Turdidæ contain a great variety of forms, and exhibit widely different characters, rendering it exceedingly difficult to arrange them in any systematic or regular sequence, or to accurately define their boundaries. In the Birds of North America, the Mocking Thrushes were placed among the Wrens, on account of the distinct tarsal scutellæ, and other characters. We are now, however, inclined to believe, with Dr. Sclater, that their place is with the recognized Turdidæ; and, among other reasons, on the ground of their more deeply cleft toes, and greater extension forward of frontal feathers. The following synopsis of the North American forms will serve the purpose of determining the genera, even if these are not arranged or combined in a strictly natural manner.
A. Turdinæ.—Tarsus covered anteriorly with a continuous plate without scales.
Wings decidedly longer than the tail, which is nearly even. Bill considerably shorter than the head.
First quill usually not one fourth the second. Wings pointed. Tarsus hardly the length of head, but yet longer than middle toe; outstretched toes falling short of tip of tail … Turdus.
B. Miminæ.—Tarsi scutellate anteriorly; scales seven.
Wings decidedly longer than the tail, which is nearly even. Tarsus as long as the head.
Bill decidedly shorter than the head, scarcely notched; wings pointed; first quill less than half the second, third and fourth longest. Claws not peculiar. Bristles prominent. Tarsus considerably longer than middle toe and claw … Oreoscoptes.
Wings decidedly shorter than the tail, which is considerably graduated; first quill half or more than half the second.
Bill notched at tip, shorter than head; straight.