title: Composition, Shell Strength, and Metabolizable Energy of Mulinia lateralis and Ischadium recurvum as Food for Wintering Surf Scoters (Melanitta perspicillata).
abstract: Decline in surf scoter (Melanitta perspicillata) waterfowl populations wintering in the Chesapeake Bay has been associated with changes in the availability of benthic bivalves. The Bay has become more eutrophic, causing changes in the benthos available to surf scoters. The subsequent decline in oyster beds (Crassostrea virginica) has reduced the hard substrate needed by the hooked mussel (Ischadium recurvum), one of the primary prey items for surf scoters, causing the surf scoter to switch to a more opportune species, the dwarf surfclam (Mulinia lateralis). The composition (macronutrients, minerals, and amino acids), shell strength (N), and metabolizable energy (kJ) of these prey items were quantified to determine the relative foraging values for wintering scoters. Pooled samples of each prey item were analyzed to determine composition. Shell strength (N) was measured using a shell crack compression test. Total collection digestibility trials were conducted on eight captive surf scoters. For the prey size range commonly consumed by surf scoters (6-12 mm for M. lateralis and 18-24 mm for I. recurvum), I. recurvum contained higher ash, protein, lipid, and energy per individual organism than M. lateralis. I. recurvum required significantly greater force to crack the shell relative to M. lateralis. No difference in metabolized energy was observed for these prey items in wintering surf scoters, despite I. recurvum's higher ash content and harder shell than M. lateralis. Therefore, wintering surf scoters were able to obtain the same amount of energy from each prey item, implying that they can sustain themselves if forced to switch prey.
authors.affiliation: USGS Patuxent Wildlife Research Center, 12100 Beech Forest Rd., Laurel, Maryland, 20708, United States of America.
authors.forename: Alicia M
authors.initials: AM
authors.lastname: Wells-Berlin
authors.affiliation: USGS Patuxent Wildlife Research Center, 12100 Beech Forest Rd., Laurel, Maryland, 20708, United States of America.
authors.forename: Matthew C
authors.initials: MC
authors.lastname: Perry
authors.affiliation: Department of Animal and Avian Sciences, University of Maryland, 4150 Animal Sciences Bldg, College Park, Maryland, 20742-2311, United States of America.
authors.forename: Richard A
authors.initials: RA
authors.lastname: Kohn
authors.affiliation: Marine & Estuarine-Environmental Science Program, University of Maryland, 0105 Cole Student Activities Bldg, College Park, Maryland, 20742-5511, United States of America.
authors.forename: Kennedy T
authors.initials: KT
authors.lastname: Paynter
authors.affiliation: Department of Animal and Avian Sciences, University of Maryland, 4150 Animal Sciences Bldg, College Park, Maryland, 20742-2311, United States of America.
authors.forename: Mary Ann
authors.initials: MA
authors.lastname: Ottinger
mesh_terms: D000818:Animals; D046090:Anseriformes / Q000378:metabolism*; D004372:Ducks; D004734:Energy Metabolism; D049879:Mytilidae / Q000737:chemistry / Q000378:metabolism; D012621:Seasons