About half a dozen of these birds fed on the fennel seeds in the Burrowing Owl Sanctuary, joining the list of feathered creatures who take advantage of the marathon plant‘s late season bounty. I’m taking a little bit of a chance identifying this bird as a Yellow-rumped Warbler, considering that the wings are totally hiding the yellow rump in these images. That aside, the size, the shape, the beak, the white wing edges, the brown streaks on the back, and the ring around the eyes all say warbler, and the yellow-rumped (aka “butterbutt”) is a common visitor here in this season.
These birds are notable for their versatility. Many birds of their size prefer to eat either bugs or berries/seeds and go away if their choice is not available. Not the YRWA. It will feast on bugs where there are bugs, and on berries and seeds where berries and seeds grow. It can even digest the wax on many berry coatings, allowing it to survive northerly winters. It also thrives on the seeds of poison ivy and poison oak without ill effects.