| Summary: | 31 p. Dunlin (Calidris alpina) were observed on a mudflat in Scituate, Massachusetts during October and November 1979 to determine 1) habitat usage, 2) prey selection, and 3) effects on prey populations by Dunlin. Rather little is known about the winter ecology of shorebirds in North America (Holmes, 1966). Dunlin fed on the lower areas of the mudflats exposed at that time and near the water's edge. By direct observation, sampling of marine fauna, and analysis of fecal pellets, Dun1in were found to feed largely on Mytilus edulis and spionid and/or Scoloplos worms. Feeding rates, Dunlin counts, and invertebrate densities indicated that the Dunlin should have reduced the M. edulis population by 30% and the spionid/Scoloplos population by 12%. The M. edulis population declined during the study due to alteration of habitat not caused by Dunlin, obscuring attempts to observe the effects of Dunlin predation on M. edu1is. The spionid/Scoloplos population underwent a significant change in distribution but not in size possibly indicating that they migrated. Mya arenaria and Tellina which were also preyed on by Dunlin significantly declined during the study. Nereis, which was seen to be taken by Black-bellied Plovers (Squatarola squatarola), and Nephyts also significantly declined during the study. The feeding on M. edulis and_spionid and/or Scoloplos deviates from reports in the literature where Dunlin were found to take mostly Nereis and small amounts of other prey (Bengston & Svensson, 1964; Ehlert, 1964). Manomet Bird Observatory. Manomet, Massachusetts.
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