In July 2001 I observed predation on a bat (species unidentified) by an Acorn Woodpecker (Melanerpes formicivorus) at the Hopland Research and Extension Center in Mendocino County, California.
A population of Acorn Woodpeckers inhabits the small developed portion of the station along Parson’s Creek, nesting in the large oaks. On 15 July 2001, Zebulon Young directed my attention to a hole in the door of a barn. The hole was approximately 5 cm in diameter and 2.5 m from the ground, in an area shaded by oaks most of the day. The door is made of two-by-four framework covered on both sides with plywood; the hole went through only the exterior layer of plywood, providing access to an otherwise sealed area of about 9 cm in width, 40 cm in breadth, and >2 m in depth. Young related that he had seen the woodpecker fly to this hole, reach in, pull out a bat with its beak, and fly with it into an overhanging oak tree. He pointed out the bird, high atop a thick horizontal oak branch. I could just see the head of the woodpecker rapidly appearing and disappearing from sight. The woodpecker appeared to be striking the branch on which it stood with its beak. The tap-tapping sound that usually accompanies this behavior was absent; instead, I heard a repeated call coming from the area of the woodpecker that sounded much like the high-pitched, relatively weak call of a bat. As I watched, several other woodpeckers flew to the immediate area, landing from 4 meters to less than 1 meter away, appearing to watch the activity with great interest. The closest of these engaged in repeated bobbing. Some or all of the woodpeckers were calling. As the struggle continued I eventually saw the flapping wing and a portion of the body of the woodpecker’s prey, a small, dark, struggling bat.