ID Help - possible Warbler

I shot this fellow this morning at San Joaquin Wildlife Sanctuary in Southern California. Looking at the bill, I do not think it is a finch or sparrow, maybe a Warbler. I have a shot of his front if needed.

Yellow-rumped Warbler (Audubon's form). Common in winter.

I'd guess Yellow-rumped of the "Audubon's" variety (female specifically) based on the yellow beneath the bill.