> Kaufman in "Advanced Birding" says that the most consistent character at
> all seasons is the bill color: in Western (dull greenish yellow); in Clark's
> (bright orange-yellow).

This field mark sounds subtle, but I will agree that it's one of the best
for separating these two. I've spotted Clark's grebes at quite a distance
because their bill is very orangy, quite unlike the western. This is one
instance where it's important to know what the "common" species looks
like. Start noting bill color on westerns when you're out and about
this winter......

Mike Donahue
Seattle