Ever seen a swift that seemed a little bit funny, and maybe you thought it might be a Vaux's Swift (if you live in the East) or a Chimney Swift (if you live in the West)? How do you really ID either one if they are out of range? How would you identify an odd, especially silent Chaetura swift?
Kevin Karlson has posted some photos comparing Chimney and a supposed Vaux's Swift online here. Chimney is on the right, Vaux's on the left.
Seems pretty obvious, right? Then take a look at the second photo. Tougher?
Kevin's description of the differences is on the ID Frontiers listserv (5 Oct 2010).
David Sibley has a new discussion on this on his own blog.