The Yellow-rumped Warbler comes in two varieties. Audubon's has a yellow throat, and Myrtle's (pictured here) has a white throat. Both have similar behavior, however their songs do differ slightly.
This little guy was all Warbler, didn't stop moving for more than a few seconds. Gives a guy with a digiscope a run for his money! Finally got him half decent in the end though. Yay!