Well, very gray tone appears to rule out Cordilleran (and Yellow-bellied). The mostly dark lower mandible doesn't fit Traill's. The short primaries aren't really right for Hammond's (or Acadian). The wingbars and tertial edges seem rather dull, although they don't appear very worn -- that would seem to rule out Least. And there's too much dark on the bill for Gray, which leaves us with a tentative (always with silent Empids, often even in hand) Dusky.