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I used hydrological data and surveys of breeding piping plover (Charadrius melodus) from 1988 to 1997 to assess the relationship of water levels to piping plover breeding distribution, abundance, and habitat use in North Dakota. Piping plover abundance at wetlands surveyed in all years (n = 48) increased significantly as wetness increased (r = 0.93, P < 0.001). However, individual wetland sites often differed in their response to hydrological conditions with some sites showing significant decreases in piping plover abundance during wet periods. The abundance of piping plovers using the Missouri River system (Oahe and Sakakawea reservoirs and the free-flowing reaches of the river) correlated strongly with upland populations of piping plovers during periods of below-average water levels in the riverine system; however, once water levels within the Missouri River system reach a certain point the relationship turned negative with river populations·of piping plovers decreasing and upland populations of piping plovers increasing.