Kutky Park behind our house is overrun with warblers right now! This looks more like a vireo to my eye-in-training... It was eating bugs in a tree near the creek. Approx 4", about 6:30 in the evening on May 11, 2011. Seemed quite comfortable eating in any orientation, including upside down.
Hi Steve- The thin, pointed beak looks more like a wood-warbler than a vireo, which tend to have thicker beaks with a slight hook on the end. i would say this is a Tennessee Warbler because of the grey head, strong white eye-line (supercilium), bright green back, white underneath, no wing-bars.