Identifying a Bird's Nest

I was out crawling around in the scrub oaks looking for mushrooms earlier, and I found this nest.  (As for mushrooms, a few elderly Shaggy Parasols were all there were.)

I checked with a more knowledgeable birder, who said, "Building a nest hanging in the fork of a tree branch like that is consistent with several vireo species."

And I had seen and heard some Plumbeous Vireos (the common ones here) nearby earlier in the summer.

I'll call that an ID.

Until 1997, Plumbeous, Cassin's, and Blue-headed Vireos were all lumped as "Solitary Vireos." Such edicts from the Big Bird Cabal help support the field guide-publishing industry.