dfabbott@compuserve.com (David Abbott) sent this comment:

It is well-known the difficulties in field separation of Western and Eastern Wood-Pewees. Useful is the combination of five or more of the following:

Western vs. Eastern

Gray-brown plumage with strong brown wash. Complete lack of Eastern's green or olive tones.

Mantle solid uniform without contrast including back, rump and uppertail coverts (unlike contrast of Eastern).

Bill mostly dark, especially lower mandible (overlap complete, however). Lower mandible > 50 % dark distally indicates Western (no Eastern in the Smithsonian showed that much dark to lower mandible). Eastern lower mandible often with sharp black tip. Western bill averages shorter with finer tip and smaller hook.

Brown throat without yellow or white. No contrast with face.

Sooty cap, dark lores.

Brown auriculars contrast with cap. Eastern tends to show auriculars and cap same color.

Western shows very angular head, with moderate crest. Bristly hind neck. Recalls larger Olive-sided.

Complete dusky-brown breast band. Little contrast with throat. Breast not subdivided in middle by whitish or yellowish bar, as in Eastern. Flanks and sides dark sooty-brown with brown watery, blurry streaks toward lower sides.

Undertail coverts with strong dusky streaks.

Wingbars very indistinct. Upper less prominent, more brown, than lower. Wings with brown cast. Tertails distinctly fringed and more obvious than wingbars. Eastern has wingbars more distinct than tertail fringing.

Tail looks short in proportion to body. Primary extension long. From below, primary extension is beyond undertail coverts.

Western has long uppertail coverts that reach the midway point of primary extension. Eastern has shorter uppertail coverts that reach the tertail tips.