Validating macroinvertebrate assumptions of the shorebird management modelfor the lower Mississippi Valley

Partners in Plight (PIF), a consortium concerned with migratory bird conser vation, has developed an energetics model to predict habitat needs for migr atory shorebirds in the Lower Mississippi Alluvial Valley (LMAV). Predictio ns are based on assumptions of benthic macroinvertebrate community composit ion and standing-stock, biomass, although little is known about these param eters in LMAV shorebird habitats. To validate several macroinvertebrate ass umptions contained in the PIF model, we assessed benthic community composit ion, abundance, and biomass for 2 shorebird habitats (mudflats in diked imp oundments and sewage settling lagoons) in western Tennessee during the fall peak of shorebird migration. Mudflats supported crustaceans, worms (Oligoc haeta), water boatmen (Hemiptera: Corixidae), mayflies (Ephemeroptera: Baet idae), and biting midges (Diptera: Ceratopogonidae); whereas settling lagoo ns were dominated by moth flies (Diptura: Psychodidae). Chironomid midges a ccounted for less than 3% of the biomass in the mudflat community, although they are gen era[ly believed to be the principal macroinvertebrate in shor ebird habitats. We detected no difference in total benthic abundance betwee n the 2 habitats; however, standing-stock biomass differed significantly (P =0.025) between settling lagoons (5.00+/-3.33 g/m(2)) and mudflats (2.17+/- 1.27 g/m(2)). We incorporated these data into the PIF energetics model, and results were remarkably similar to the original model predictions. Althoug h other parameters of the PIF model still require testing and more informat ion is needed to understand shorebird-macro invertebrate dynamics, results of th is study validate model assumptions concerning resource availability for migratory shorebirds in the LMAV.