Report 31631: Nature photogapher hears possible woodknocks on Skyline Drive

I was in the Shenandoah National Park, on Skyline Drive. I had stopped at one of two overlooks (they are only about 2.5 miles apart) in order to take photos of the sunset. The Park Service closes Skyline Dr. during the Virginia hunting season at 5:00 PM, so most of the visitors had already left. At a few minutes to five, as I was preparing to put my camera away, I was just standing, watching the changing sky. Downhill, and across an open area in front of the overlook, I heard two quick knocks come from the woods. About 30 seconds later, and several hundred yards to the right of the knocks, I heard one more come from the woods. About a minute later, two more knocks came from behind me, uphill and to my left. Unsure of the county lines in this area, but it would be in either Greene or Rockingham County. I am a frequent visitor to the Park, and had not heard anything like this before.