The young of this species do not acquire the brown colour of the head until the approach of spring, when no difference is observable between the sexes.
Sitta pusilla, Lath. Ind. Ornith. vol. i. p. 263.—Ch. Bonaparte, Synops. of Birds of the United States, p. 97.
Brown-headed Nuthatch, Sitta pusilla, Wils. Amer. Ornith. vol. ii. p. 105. pl. 15. fig. 2.—Nuttall, Manual, vol. i. p. 584.
Adult Male. Plate CXXV. Fig. 1.
Bill of moderate length, strong, subconical, compressed, the tip abrupt and wedge-shaped; upper mandible slightly convex in the dorsal outline, the sides sloping, the edges acute; dorsal outline of lower mandible straight. Nostrils basal, lateral, oblong. General form short and robust. Feet rather short and strong; tarsus compressed, anteriorly scutellate, behind sharp; toes free, scutellate above, the hind toe strong; claws arched, compressed, acute, that of the hind toe large.
Plumage soft and blended; wings of ordinary length, the second, third, and fourth quills longest. Tail short, even, of twelve rounded feathers.
Bill brownish-black above, and on the tips of the lower mandible, the base of which is light greyish-blue. Iris hazel. Feet dusky brown. The general colour of the plumage above is dull leaden grey; the two middle tail-feathers of the same tint; the rest black, the margin of the outermost and the ends of it, and of the three next on each side, white, the tips grey. Upper part of the head and hind-neck light reddish-brown, with a white spot on the hind-neck. The under parts in general are dull white.
Length 4 inches, extent of wings 8; bill along the back 5⁄12, along the edge 7⁄12; tarsus 8⁄12.
Adult Female. Plate CXXV. Fig. 2.
The female has the tints paler, but in other respects resembles the male.