C. borealis. Upper half of nasal tufts white. Black spectacle bordered above the ear-coverts by hoary whitish. Scapulars and upper tail-coverts approaching white. Wing, 4.70; tail, 4.70; tarsus, .93. Hab. Arctic America; in winter south into United States, especially into the northern portions.
b. No white crescent on lower eyelid. Beneath without bars, except in young. Tarsus more than 1.00; wing less than 4.50.
C. ludovicianus. Black spectacle not bordered over ear-coverts with whitish.
White patch on primaries reaching nearly as far as end of first quill. Nasal tufts entirely black.
Black of lores and nasal tufts bordered above with hoary whitish. Tail white at base; inner webs of secondaries paler toward margin, but not abruptly white. Beneath entirely white, without ashy tinge laterally, or across breast. Axillars whitish. Upper tail-coverts ashy-white, scapulars pure white. Wing, 4.10; tail, 4.20; tarsus, 1.10; bill, .50. Hab. Western North America from Pacific Coast east to a little beyond the Mississippi, and to Texas. Nearly all of Mexico … var. excubitoroides.
Black of lores, etc., not bordered above by whitish. Tail black at base. Inner webs of secondaries pure white to the shaft on basal half. Beneath tinged with ashy laterally and across breast. Scapulars and upper tail-coverts hardly different from back. Bill, .60. Hab. California and fur countries … var. robustus.
White patch on primaries reaching only about half-way to end of first quill. Nasal tufts hoary-grayish above.
Black of lores bordered above by hoary-whitish. Tail as in elegans,—secondaries as in excubitoroides. Beneath very strongly tinged with plumbeous laterally and across breast. Upper tail-coverts like the back, posterior scapulars only inclining to white. Axillars plumbeous. Wing, 3.80; tail, 3.95; tarsus, 1.00; bill, .50. Hab. South Atlantic and Gulf States … var. ludovicianus.
We now proceed to give a more detailed table of these species, and under the heading of each shall omit any further description:—
General Color. Bluish or plumbeous ash above; the outer edges of scapulars, sometimes the forehead and rump, paler. Beneath white, sometimes with waved transverse dark lines. A broad black stripe from side of upper bill through eye (extending more widely beneath than above it, sometimes wanting above) to end of ear-coverts. Wings (except lesser coverts) and tail black; the former with a white patch across base of primaries, sometimes on inner webs of secondaries; the secondaries tipped with white; the tail with broad white tips to the lateral feathers, the concealed bases of which are also usually white.