Family XIII. MOTACILLINAE. WAGTAILS.
Bill of moderate length, straight, slender, a little broader than high at
the base, compressed toward the end; upper mandible with the dorsal line
sloping, a little convex toward the end, the nostrils slight, the tip acute;
lower mandible with the angle rather long and narrow, the dorsal line ascending
and scarcely convex, the edges somewhat involute, the tip acute. General form
slender; head ovato-oblong; neck short. Feet of ordinary length, slender; toes
very slender, the lateral equal, the outer adherent at the base, the hind toe
rather large; claws rather long, arched, compressed, acute, that of the hind toe
generally very long. Plumage soft and blended. Bristles small. Wings long and
pointed, one of the minor secondaries often much elongated and tapering. Tongue
sagittate, slender, with the tip slit; oesophagus uniform; stomach a very
muscular gizzard, roundish, with large tendons, and thin rugous epithelium,
intestine of moderate length; coeca very small. Trachea simple, with four pairs
of inferior laryngeal muscles.
This family is connected with the Turdinae by Seiurus, and with the Alaudinae by Anthus, which are the only two American genera.