Wilson's Warbler

I've had repeated run-ins with this Warbler now in Arizona as well as California. I still have been unable to get a better picture, even though this bird is common during migratory periods and is not overly shy. For the moment, the Wilson's Warbler is my official nemesis. Every Ahab needs his White Whale (or little yellow bird).

This is the closest I've come. I actually had the bird in focus, but of course there's a heavy shadow obscuring the face.