Woodpecker

 An Acorn Woodpecker, Madera Canyon AZ.

From what I have read, they are medium-sized for a woodpecker.  They can mostly be found in mixed oak-conifer forest, like in Madera Canyon AZ.  Their range in the US is along the west coast and along the Arizona New Mexico border.  There is also a small area of Texas with some.  

They are in large groups and store acorns in tree trunks and telephone poles.