Invertebrate abundance at occupied and potential piping plover nesting beaches: Great Plains alkali wetlands vs. the Great Lakes

Abstract

We assessed the potential for reestablishment of endangered piping plovers (Charadrius melodus) at selected Great Lakes beaches by comparing invertebrate biomass and abundance with that at alkali wetland beaches occupied by breeding plovers in the Great Plains. We measured invertebrate occurrence using sticky traps secured to beach foraging substrates. Diptera (especially Chironomidae and Ephydridae) comprised from 45 to 99% of invertebrate abundance and 24 to 53% of the biomass at six separate sites in the Great Lakes. Coleoptera (<1–17% abundance; 28–54% biomass) and Hymenoptera (<1–10% abundance; <1–9% biomass) also were frequently detected on beaches at the Great Lakes sites. At alkali wetland beaches in North Dakota, Diptera (Ephydridae and Chironomidae) comprised 95% of the invertebrate fauna numerically and made up more than 80% of the biomass. The mean invertebrate biomass at two Great Lakes beaches (Plate Bay, MI=0.16 g/m2/hr, Long Island, WI=0.11 g/m2/hr) was similar (P<0.05) to that at North Dakota alkali beaches (0.09 g/m2/1hr) occupied by breeding piping plovers. However, at four other Great Lakes beaches, we measured 3 to 6 times less (0.01–0.02 g/m2/hr; P<0.01) invertebrate biomass than at the alkali wetland beaches. Mean invertebrate abundance showed similar patterns among the sites. Food availability may limit the reestablishment of piping plovers at some Great Lakes beaches. We recommend that invertebrate abundance and biomass be measured at currently occupied piping plover nesting areas in the Great Lakes and be assessed at any sites proposed for reintroduction of piping plovers.