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In the spring, male Ruffed Grouse perch on fallen logs and make a low-pitched drumming sound by opening and closing their wings in rapid succession. The thumping starts slow but quickly gains in speed, and the rapidly beating wings turn into a complete blur when the drumroll reaches its peak. One might think the thumps are produced by the beating of the wings against the chest, but in actuality the thumps are little sonic booms created as air suddenly fills a vacuum made when the wings are thrust
