Strange bird in the park--ID question

This morning I saw a bird in a pine park near my house and I couldn’t identify the species. It was alone in a pine tree and it resembled an Oregon Junco (dark head, grayish back, off white undersides, and a pale bill.) However it was too small to be a junco; it was closer in size to a kinglet or bushtit (about 4 to 4.5 inches.) Neither kinglets nor bushtits have dark heads and I’m fairly certain it was not a chickadee or a nuthatch because they have white on their faces and also because it didn’t act like one of those. It hopped about in the tree making a high pitched chirp, then flew off to another tree where I lost sight of it. I think it’s been in the area for several days but this is the first time I’ve gotten a decent look at it.

As I can’t find it in the birds of North America field guide I’ve considered the possibility that it might be an escaped exotic. Any help would be appreciated.

A small finchlike bird could well be some species of munia. There are a lot of them, and many are kept as pets. Offhand I’m not sure if any the species in the pet trade in the US match the description of your bird.

Pygmy Nuthatch, rather than the more common Red-Breasted or White-Breated? The habitat, size, and noisiness fit, and in the right light the head might appear to be darker than the body.