Answer:

This bird can immediately be narrowed down to the Passerines. Structurewise, it appears to be small, with a short tail and perhaps chunky build — we have sparrows, finches, warblers, and vireos with a similar shape but that doesn’t narrow it down too much. Sparrows and finches can be eliminated since none have strictly gray and white plumage. Some warblers have similarly colored bodies, but have either unmarked wings (Lucy’s or Virginia’s), streaks below (Black-throated Gray), or lack a solid gray crown and face (Hermit). That leaves us with the vireos.

Our eyes are drawn towards its head, where we can just barely make out a white eye ring and a lack of a broad supercilium, and when coupled with two bold white wing bars, narrows it down to five ABA area vireos — Hutton’s, Black-capped, Cassin’s, Blue-headed, and Plumbeous, the latter three composing the former species, the “Solitary Vireo” Hutton’s can be eliminated due to the lack of any olive tinge to the tail, underparts, or upperparts. A vagrant Black-capped Vireo can be eliminated by the lack of a contrasting black head and olive back as our bird is uniformly gray above. In addition, that species has never been observed in California, but vagrants have shown up as far north as Quebec and as close as Tuscon in the 1970s. Moving on to the “Solitary Vireo” complex, Blue-headed can be eliminated by the lack of contrast between head and back, along with the overall lack of olive. This leaves Cassin’s or Plumbeous.

Neither are common in the LA Basin, but during spring migration, Cassin’s is more prevalent, while in fall migration and through winter, Plumbeous is the more widespread of the two. Cassin’s typically show more olive in their underparts, with olive tinged flanks or undertail coverts. The completely gray and white coloration points to Plumbeous, and while the dullest Cassin’s shows some overlap with the brightest Plumbeous, this bird lacks any olive tinge in the undertail coverts and flanks, which bright Plumbeous and dull Cassin’s typically share. This bird was photographed at Ken Malloy Harbor Regional Park on November 23, 2022 and is a Plumbeous Vireo.

Congratulations to Jake, Andy, and Ava for figuring out Plumbeous Vireo!