Gen. Char. Plumage soft and loose. Bill as long as head, not notched, compressed; all its lateral outlines decurved. Nostrils not overhung by feathers, linear, with an incumbent thickened scale, as in Troglodytes. No rictal bristles, and the loral and frontal feathers smooth, without bristly shafts. Tarsus scutellate anteriorly, shorter than middle toe, which again is shorter than hind toe. All claws very long, much curved and compressed; outer lateral toe much the longer; basal joint of middle toe entirely adherent to adjacent ones. Wings rather pointed, about equal to the tail, the feathers of which are much pointed, with stiffened shafts. Primaries ten; first less than half the second. Nest in holes of trees; eggs white, sprinkled with reddish.
Certhia americana.
Of the Certhiadæ but one genus belongs to America,—Certhia, with its one small species of considerable variability with locality. The characters above given include both family and generic characters, derived from this one genus. This is readily distinguished by the decurved, compressed bill; absence of notch and bristles; exposed linear nostrils with incumbent scales; connate middle toe, very long claws, short tarsi, pointed and stiffened tail-feathers, etc.
The American and European varieties (they can scarcely be called species) resemble each other very closely, though they appear to be distinguished by such differences as the following:—
The two European races, C. familiaris and C. costæ, both differ from all the American varieties in having the crissum scarcely tinged with yellowish.
C. familiaris is more ashy beneath than any others, and C. costæ is purest white beneath of all. Nearest C. familiaris, in the American series, as regards tints of the upper parts, are the Pacific coast specimens of C. americana,—while the latter are most like the Atlantic region specimens of the same. C. mexicana is to be compared only with the North American forms, though it is the only one approaching familiaris in the ashy lower parts.
C. familiaris is at once separated from the rest by having the tail shorter than the wing.
C. costæ is almost precisely like Eastern specimens of C. americana in colors, but is absolutely pure white below, and without the distinctly yellowish crissum of the American bird. The bill and claws, however, are considerably longer than in Eastern americana, though their size is almost equalled by those of Western specimens; the colors are, however, more decidedly different.
There is never any deviation from the generic pattern of coloration; but the variation, among individuals of each form, in length of the bill and claws, as well as the tail, is remarkable.