Gen. Char. Tarsus very short, but stout; less than the middle toe and scarcely longer than the hinder; considerably less than the culmen. Bill quite broad at the base; wider than half the culmen. Tail moderately forked. Wings very long and much pointed, reaching beyond the middle of the tail; the first primary about equal to the fourth. All the primaries slender and rather acute, but not attenuated. Head moderately crested. Color olive above, pale yellowish beneath, with a darker patch on the sides of the breast. Under tail-coverts streaked in most species. A tuft of cottony-white feathers on each side of the rump (concealed in most species).
This genus is pre-eminently characterized among North American Flycatchers by the very short tarsi, and the long and much pointed wings.
In most other genera, as Sayoris, Myiarchus, and Empidonax, a trace of a cottony tuft may be discovered by careful search on the flanks; but in the present genus, there is, in addition, the tufts on the rump, not found in the others. The species are as follows:—
Species and Varieties.
A. Cottony patch of white feathers on sides of the rump greatly developed, and conspicuous. Rictal bristles very short (about one fourth the length of the bill). Lower parts distinctly and abruptly white medially (somewhat interrupted on the breast).
1. C. borealis. First quill longer than the fourth, generally exceeding the third. Wing, 4.00 to 4.40; tail, 2.90 to 3.00; culmen, .90; tarsus, .60. Above dark olive-plumbeous, the tertials edged with whitish; lower parts a lighter shade of the same, laterally and across the breast (narrowly), the throat and middle line of the abdomen being abruptly white. Young not different. Hab. Northern parts of North America, to the north border of United States; on the mountain-ranges, farther south, on the interior ranges, penetrating through Mexico to Costa Rica.
B. Cottony patch on side of rump rudimentary and concealed. Rictal bristles strong (one half, or more, the length of the bill). Lower parts not distinctly white medially.
a. First primary shorter than fifth, but exceeding the sixth. Tail shorter than wings.
2. C. pertinax. Wing more than 3.50. Grayish-olive, becoming lighter on the throat (indistinctly) and abdomen (decidedly). No distinct light bands on the wing. Rictal bristles about half the length of bill.
The olive of a grayish cast, and not darker on the crown. Wing, 4.45; tail, 3.90; depth of its fork, .35; culmen, .92; tarsus, .70. Hab. Mexico, generally north into Arizona (Fort Whipple, Coues) … var. pertinax.