1. B. virginianus. Lower parts transversely barred with black, and without longitudinal stripes. Above without longitudinal stripes on the anterior portions.
a. A conspicuous patch of white on the jugulum; lining of the wing immaculate, or only faintly barred. Wing, 14.00–16.00; tail, 8.00–10.00; culmen, 1.10–1.20; tarsus, 2.00–2.20; middle toe, 1.95–2.10.
Rufous tints of the plumage prevailing; face dingy rufous. Hab. Atlantic Province of North America … var. virginianus.
Lighter tints of the plumage prevailing; face dirty or fulvous white. All the colors lighter. Hab. Western Province of United States, and interior regions of British America. Upper Mississippi Valley in winter (Wisconsin, Hoy; Pekin, Illinois, Museum, Cambridge) … var. arcticus.
Dusky tints of the plumage prevailing; face dull grayish, barred with dusky. All the colors darker, chiefly brownish-black and grayish-white, with little or no rufous. Hab. Littoral regions of northern North America, from Oregon northward, and around the northern coast to Labrador … var. pacificus.
b. No conspicuous patch of white on the jugulum, which, with the lining of the wing, is distinctly barred with blackish. Wing, 12.00; tail, 7.50; culmen, 1.00; tarsus, 2.10; middle toe, 1.85.
Colors much as in var. virginianus, but more densely barred beneath, the dark bars narrower and closer together. Hab. South America … var. magellanicus.[27]
2. B. mexicanus.[28] Lower parts longitudinally striped with black, and without transverse bars. Above with longitudinal stripes on the anterior portions. Wing, 11.20–12.00; tail, 6.00–6.50; culmen, .90; tarsus, 2.00; middle toe, 1.95. Hab. Middle and South America generally.
Subgenus NYCTEA, Stephens.
Nyctea, Stephens, Cont. Shaw’s Zoöl. XIII, 62, 1826. (Type Strix nyctea, Linn. N. Scandiaca, Linn.).