The Hairy Woodpecker is virtually identical in plumage pattern to the smaller Downy Woodpecker, but it can be distinguished from the Downy Woodpecker by the absence of black spots on the underside of its white tail feathers and the length of its bill.
The Hairy Woodpecker's bill is approximately equal to its head length, whereas the Downy Woodpecker's bill is much shorter than its head.

First 3 photos: Rio Grande Nature Center State Park, Albuquerque, New Mexico, USA, 15 January 2019
Last 2 photos: Sandia Crest, Albuquerque, New Mexico, USA, 16 January 2019