Toward the end of the hike, when we were again down on the main part of the park, I came upon a tree riddled with holes. In each hole was an acorn. There were red-headed Acorn Woodpeckers in the tree, so I looked them up.
At a website by Don Roberson, a great bird photographer from the Monterey area, I found a really good picture:http://creagrus.home.montereybay.com/woodpeckers.html. The Acorn is the third photo down. Here is the tree I saw:
And the whole tree: