The Acorn Woodpecker, Melanerpes formicivorus, is a common California bird of the oak woodland. These woodpeckers will drill holes in trees, fenceposts, telephone poles, and even sides of houses to store acorns during the lean times of winter. Many of these trees have been used for decades by many generations of birds. As you search for this hide, look around at some of the trees. There is a large foothill pine, Pinus sabiniana, nearby that is riddled with holes.