Bill much shorter than head (exposed culmen about as long as hallux, without claw), narrowly conoidal in lateral profile, its depth at base of exposed culmen equal to less than half the length of the latter; culmen flattened, very slightly to moderately decurved terminally, more or less distinctly depressed in middle portion, the basal half (mesorhinium) more compressed and more or less distinctly elevated or arched; gonys longer than mandibular rami, more than half as long as exposed culmen, rounded, slightly but distinctly convex; maxillary tomium more or less distinctly notched subterminally. Nostril narrowly cuneate or linear, longitudinal, overhung by a broad operculum. No rictal, frontal, nor mental bristles. Wing excessively rounded, very concave beneath; sixth, fifth, and seventh primaries longest (nearly equal in length), the tenth (outermost) more than half as long as the longest; all the remiges very broad, rather soft in texture; longest secondaries extending beyond tip of ninth primary. Tail decidedly to much shorter than wing to end of secondaries, excessively graduated, the rectrices (10 in number) very broad, soft, with webs semi-decomposed. Tarsus much less than half as long as wing (about twice as long as bill), its scutellation taxaspidean or semi-holaspidean (the outer series of plantar scutella much broader than the inner); middle toe, without claw, decidedly shorter than tarsus (about as long or slightly longer with claw); lateral toes about equal in length, reaching (without claw) to or very slightly beyond penultimate articulation of middle toe; hallux (without claw) longer than lateral toes and much stouter, its strongly arched claw shorter than the digit; outer toe united to middle toe only at extreme base, the inner toe entirely separated. Plumage compact but very soft (almost silky), that of the rump and flanks more elongated and lax.
Coloration. — Adult males nearly uniform gray or dusky, with hinder parts more or less rufescent and (usually) barred, sometimes with the forehead silvery gray, some species with throat or throat and breast white; adult females similar but duller in color and more barred; young very different, rusty or brown prevailing, conspicuously barred.
Nidification. — "The nest is placed in a mass of moss on a bank; it is also composed entirely of moss. The female lays two eggs, large for the size of the bird, and white." (S. magellanicus Salmon, Proc. Zool. Soc. Lond., 1879, 528.)
Range. — High mountains of Costa Rica to Falkland Islands, southern Chile and Argentina, southeastern Brazil, and mountains of Venezuela. (About eighteen species and subspecies known.)
