Possible knocking heard by hikers in the Chilliwack valley witnessed in British Columbia, Canada

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At approximately 10 am my hiking partner and myself had packed up our camp after a chilly nights stay at Lindeman Lake in the Chilliwack River Valley. We had hiked about 15 minutes from our camp, down the main trail (headed back to the parking lot). I was about 40 feet infront of my partner and started hearing banging noises coming from the trees to the North of us. I stopped and listened. As my partner caught up to me I asked if he had heard the noises as well. He stated that he thought they were from me. I said no and we both stopped and listened as the banging sounds continued. We heard "tap, tap, tap" It sounded like two rocks banging together -- definitely not wood or a woodpecker, as this obviously crossed my mind. He said it definitely is stones. The sounds came from about 70-100 feet from us in the trees and were relatively timed out as it takes a certain amount of time to make strikes. (I tested this much farther down the trail). As the banging continued I realized they we...