Female Downy Woodpecker Excavating - Nov. 2010
THIS is the nest that you'll see in the following photos taken in May 2013, 17 months later by a Nuttall's and then a Tree Swallow.
Woodpeckers: Downey, Nuttall's, Sapsuckers
I know this is going way back, but I'd say this is a Downy rather than a Nuttal's. See the white strip down the back? Maybe the Downy was using a Nuttal's nest?