Habits. Mr. Salvin found the Mexican Tree-Creeper by no means uncommon in the pine forests of the upper zone of the Volcan de Fuego. He also observed it frequenting pine-trees in the district of Chilasco, Vera Paz, at about 6,000 feet above the sea.
Family TROGLODYTIDÆ.—The Wrens.
Char. Rictal bristles wanting; the loral feathers with bristly points; the frontal feathers generally not reaching to nostrils. Nostrils varied, exposed or not covered by feathers, and generally overhung by a scale-like membrane. Bill usually without notch (except in some Middle American genera). Wings much rounded, about equal to tail, which is graduated. Primaries ten, the first generally about half the second. Basal joint of middle toe usually united to half the basal joint of inner, and the whole of that of the outer, or more. Lateral toes about equal, or the outer a little the longer. Tarsi scutellate.
The impossibility of defining any large group of animals, so as to separate it stringently and abruptly from all others, is well understood among naturalists; and the Troglodytidæ form no exception to the rule. Some bear so close a resemblance to the Mocking Thrushes as to have been combined with them; while others again exhibit a close approximation to other subfamilies. The general affinities of the family, however, appear to be to the Turdidæ, and one of the best characters for separating the two families appears to exist in the structure of the feet.
In the Turdidæ the basal joint of the outer lateral toe is united to the middle toe, sometimes only a part of it; and the inner toe is cleft almost to its very base, so as to be opposable to the hind toe, separate from the others. In the Troglodytidæ, on the contrary, the inner toe is united by half its basal joint to the middle toe, sometimes by the whole of this joint; and the second joint of the outer toe enters wholly or partially into this union, instead of the basal joint only. In addition to this character, the open, exposed nostrils, the usually lengthened bill, the generally equal lateral toes, the short rounded wings, the graduated tail, etc., furnish points of distinction.
Genera.
A. Lateral toes very unequal.
a. Culmen depressed basally, the interval between the nostrils wider than the much compressed anterior half of the bill. Plate on the posterior half of the tarsus continuous. Catherpes.
b. Culmen compressed basally, the interval between the nostrils narrower than the rather depressed anterior half of the bill. Plate on the posterior half of the tarsus broken into smaller scales. Salpinctes.