Species and Varieties.
P. arcticus. Dorsal region without white markings; no supraloral white stripe or streak, nor nuchal band of white. Four middle tail-feathers wholly black; the next pair with the basal half black; the outer two pairs almost wholly white, without any dark bars. Entire sides heavily banded with black; crissum immaculate; sides of the breast continuously black. ♂. Crown with a patch of yellow, varying from lemon, through gamboge, to orange, and not surrounded by any whitish markings or suffusion. ♀. Crown lustrous black, without any yellow, and destitute of white streaks or other markings. Wing, 4.85 to 5.25; tail, 3.60; culmen, 1.40 to 1.55. Hab. Northern parts of North America. In winter just within the northern border of the United States, but farther south on high mountain-ranges.
P. tridactylus. Dorsal region with white markings, of various amount and direction; a more or less distinct supraloral white streak or stripe, and a more or less apparent nuchal band of the same. Four to six middle tail-feathers entirely black; when six, the remainder are white, with distinct black bars to their ends; when four, they are white without any black bars, except occasionally a few toward the base. Sides always with black streaks or markings, but they are sometimes very sparse; crissum banded with black, or immaculate; sides of the breast not continuously black. ♂. Crown with a patch of gamboge, amber, or sulphur-yellow, surrounded by a whitish suffusion or markings. ♀. Crown without any yellow, but distinctly streaked, speckled, or suffused with whitish (very seldom plain black).
a. Six middle tail-feathers wholly black. Europe and Asia.
Sides and crissum heavily barred with black (black bars about as wide as the white ones).
Back usually transversely spotted with white; occasionally longitudinally striped with the same in Scandinavian examples. Wing, 4.80 to 5.10; tail, 3.80 to 4.00; culmen, 1.20 to 1.35. Hab. Europe … var. tridactylus.[127]
Sides and crissum almost free from black bars; black bars on the outer tail-feathers very much narrower than the white.
Back always (?) striped longitudinally with white. Wing, 4.70 to 4.75; tail, 3.65 to 3.90; culmen, 1.20 to 1.35. Hab. Siberia and Northern Russia … var. crissoleucus.[128]
b. Four middle tail-feathers, only, wholly black. North America.
Sides heavily barred with black, but crissum without bars, except beneath the surface. Three outer tail-feathers without black bars, except sometimes on the basal portion of the inner webs. Wing, 4.40 to 5.10; tail, 3.40 to 3.70; culmen, 1.10 to 1.25.