Acorn Woodpeckers (Melanerpes formicivorus) are commonly found in oak woodlands in the mountains of Arizona and California. They feed on acorns and will drill them into the Swiss cheese-like holes of a particular tree chosen to be their communal granary tree. I recently observed this female Acorn Woodpecker in the Chiricahua Mountains of southeastern Arizona.
An Acorn Woodpecker can be recognized by its black back and chest, white underparts, black bill surrounded by a ring of black feathers followed by a ring of white feathers, red crown, and white eyes.
I could tell that this Acorn Woodpecker was a female because there was a band of black between her white forehead and red crown.
There is no such band of black on a male Acorn Woodpecker, and the red of a male's crown touches the white of his forehead.
Acorn Woodpeckers have a white rump and wing patches, but these can only be seen when they are in flight and not perched like this one.
Acorn Woodpeckers normally live in large family groups, but the weather was bad, with icy winds and light snow despite the weak sunshine, so I only saw this one female Acorn Woodpecker. Luckily, she quite nicely allowed me to get several photos of her.