Similarities Between Campephilus Woodpecker Double Raps and Mechanical Sounds Produced by Duck Flocks

The search for the Ivory-billed Woodpecker (Campephilus principalis) in eastern Arkansas and northwestern Florida has yielded double raps recorded by autonomous recording units (ARUs) in White River National Wildlife Refuge and along the Choctawhatchee River, respectively. These double raps have been presented as suggestive evidence for the presence of the species in those regions. We present data comparing double raps produced by wing collisions from an aerial Gadwall (Anas strepera) flock to double raps documented by ARUs. Close similarities in amplitude ratios, peak-to-peak times between raps, and auditory quality between ARU recordings and wing collisions from a Gadwall flock illustrate the ability of flying ducks to produce sounds easily mistaken for the double raps of Campephilus woodpeckers. All ARU double raps suggesting the presence of an Ivory-billed Woodpecker should be reconsidered in light of the phenomenon of duck wingtip collisions, especially those recorded during winter months when duck flocks are common across flooded bottomlands of the southeastern United States.