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Picoides villosus
Woodpecker
I agree with Hairy Woodpecker. Downy would show black markings on the outer retrices (tail feathers).
This is either a Downy (Picoides pubescens) or Hairy (P. villosus) Woodpecker - their plumage is essentially identical (they're the only woodpeckers in North America with white backs), and the best way to tell them apart is by size, the Hairy being larger, with a longer bill, and more fond of bigger trees, while the Downy is smaller and common in gardens across the continent. It's hard to tell from this picture exactly which species this is, though.