From the Cornell website: "Red-naped Sapsuckers are industrious woodpeckers with a taste for sugar. They drill neat little rows of holes in aspen, birch, and willow to lap up the sugary sap that flows out. The presence of sap wells is a good indication that they are around, but so are their harsh wailing cries and stuttered drumming. The red patch on the back of their head helps separate these sharply dressed black-and-white sapsuckers from Yellow-bellied Sapsuckers in the East and Red-breasted Sapsuckers along the western coastal states."
This one was in Madera Canyon, AZ.