This is a female lacking the red nape of the male. Notice the all white outer tail feathers without the black baring of the similar but smaller Downy Woodpecker. These two woodpeckers are not actually each others closest relatives. Here in California where the two overlap, the Hairy prefers tree trunks while the Downy forages in smaller branches using its proportionately smaller bill. Thus they avoid direct competition by partitioning available resources. Downy usually prefers second-growth woodland while the Hairy likes larger trees. Both species exhibit parallel geographic variation with birds in Eastern North America having more white spangling on their wings while those in the far West have little or no wing spotting as seen here. Thus the two seem to mimic each other across their range. This is sometimes called interspecific social dominance mimicry (Prum, Zool J Linn Soc, 172: 910-941, 2014).
