Common Characters. Prevailing color plumbeous; abdomen, crissum, and lateral tail-feathers white.
A. Bill entirely light flesh-colored, dusky only at extreme point. Color of jugulum (deep ash or plumbeous-black) abruptly defined against the pure white of the abdomen.
a. Posterior outline of the dark color of the jugulum convex; sides pinkish.
1. J. oregonus. Back and wings more or less tinged with dark rusty, in sharp contrast with the black (♂) or ash (♀) of the head and neck. Hab. Pacific Province of North America, from Sitka southward; east across the Middle Province of United States, to the Rocky Mountains (where mixed with J. caniceps[116]) occasionally to the Plains (where mixed with J. hyemalis[117]).
b. Posterior outline of the dark color of the jugulum concave; sides ashy.
2. J. hyemalis. Back and wings without rusty tinge.
Wing without any white; three outer tail-feathers only, marked with white. Bill, .40 and .25; wing, 3.10; tail, 2.80; tarsus, .80. Hab. Eastern Province North America. Straggling west to Arizona (Coues); in the northern Rocky Mountains, mixed with J. oregonus … var. hyemalis.
Wing with two white bands (on tips of middle and greater coverts); four outer tail-feathers marked with white. Bill, .50 and .30; wing, 3.40; tail, 3.20. Hab. High mountains of Colorado (El Paso Co., Aiken) … var. aikeni.
3. J. caniceps. Back (interscapulars) rufous; scapulars and wings uniform ashy. Hab. Central Rocky Mountains of United States. (Along southern boundary mixed with J. cinereus.[118])
B. Bill with the upper mandible black, the lower yellow. Ash of the jugulum fading gradually into the grayish-white of the abdomen.