Butter butts, aka yellow-rumped warblers, aka Myrtle warblers. When they come, you know you've ben invaded. Funny thing about this year; they are all in the trees, since there are leaves and no need to hang out on the ground for your protein packed goodies. This bird made me laugh; all I saw for the first few minutes was the bird's butt - easy to see how it got it's name! And generally the only part of their anatomy that warblers like to show you anyway - undercarriage and back end. They are usually so high up that's it.