Hutton's Vireo
I had Hutton's, a PacificSlope Flycatcher and a Cassin's Vireo all within a few hours, tough job keeping up with ID's as they all look very similar.
I was pretty sure I was looking at a Golden-crowned Kinglet as it came in a wave of Chestnut-back Chickadees, however I think ithappened to pop out not really part of the wave.