Nuttall's Woodpecker, Picoides nuttallii
Nuttall's is the most common woodpecker in Silicon Valley where I live, and we often see them in our yard. They are the west coast cousin to the quite similar Ladder-backed Woodpecker of the southwest. Adult males, above, have the red patch at the rear of the crown, while adult females, below, have no red in their plumage.
A male Nuttall's excavating a new nest, like the one shown in use below.
The picture above and the two below show a sequence in which a female feeds
a male nestling, above; the relatively large patch far forward on the head identifies
the young bird as a male...
...while here the male parent at the same nest feeds a different nestling, probably
a female because of the smaller patch less far forward (young but not adult female
Nuttall's can have a red patch)...
...and here the adult male feeds an earwig to a male nestling, possibly the same
young bird shown at this nest in the picture two above, with the adult female.
Note the different positions of the adult and juvenile male patches.
This bird, a lone visitor at our back yard fountain, appears to be a juvenile male from its red patch, which extends forward beyond the eye.
A male leaving an active nest carrying debris -- wood chips left over from the excavation of the nest, and a fecal sac from a nestling.
An adult male Nuttall's feeding on Chinese pistache berries in the fall.