Bentson State Park bird feeders was the Ladder-backed Woodpecker (above), a common bird of the southwest. This "zebra-backed" woodpecker is quite similar to the Nuttall's Woodpecker (below) found in the oak woodlands California. Fortunately for birders trying to identify them, the two species' ranges barely overlap. (In the limited area of overlap, the two species have been known to hybridize.)
In my photos, the Ladder-backed Woodpecker is a male and the Nuttall's is a female--hence the red on the Ladder-back's head, which is not present on the female Nuttall's. Only one of the field marks mentioned by Sibley to separate these woodpeckers is evident in my photographs. Note the upper back on these birds. On the Ladder-backed Woodpecker, the upper back is whitish with thin black stripes. In the Nuttall's Woodpecker, in a photograph from the California coast, the upper back is solid black. Sibley's suggestion that the feathers behind the bill (the lores) are white in the Ladder-backed and buffy on the Nuttall's are not born out by my photos.