>The bander who e-mailed me claimed that the degree of overlap is
>known. The person could be wrong, of course - I'm in no position
>to judge which of you is right. Let's talk about the overlap
>between male Coops and female sharpie in western populations :)
>
According to the measurements in Pyle et al, and in Ridgway's Birds of
North and Middle America (1902??) there is some overlap, but not that much.
If the bird is at all typical for its sex in measurements, it is likely
sexable in the hand. As well, you can peek at those feather bases and get an
idea as to what it will look like in the summer. If you have time you could
just clip off a few mm. of each feather tip (only a few thousand) and bring
it into summer plumage. A light sandpaper may do the trick ;-)

Cheers,

Alvaro Jaramillo "You are better off not knowing
Half Moon Bay, CA how sausages and laws are made"
- From fortune cookie, Vancouver
alvaro at quake.net circa 1994
http://www.quake.net/~alvaro/index.html