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Wetland food resources for spring-migrating ducks in the Upper Mississippi River and Great Lakes Region

Authors

  • Jacob N. Straub,

    Corresponding author
    1. School of Environment and Natural Resources, The Ohio State University, Columbus, OH 43202, USA
    Current affiliation:
    1. Department of Wildlife, Fisheries, and Aquaculture, Mississippi State University, Mississippi State, MS 39762, USA.
    • School of Environment and Natural Resources, The Ohio State University, Columbus, OH 43202, USA
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  • Robert J. Gates,

    1. School of Environment and Natural Resources, The Ohio State University, Columbus, OH 43202, USA
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  • Richard D. Schultheis,

    1. Cooperative Wildlife Research Laboratory, Southern Illinois University, Carbondale, IL 62901, USA
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  • Tina Yerkes,

    1. Ducks Unlimited, Inc., 1220 Eisenhower Place, Ann Arbor, MI 48108, USA
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  • John M. Coluccy,

    1. Ducks Unlimited, Inc., 1220 Eisenhower Place, Ann Arbor, MI 48108, USA
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  • Joshua D. Stafford

    1. Frank C. Bellrose Waterfowl Research Center, Illinois Natural History Survey, Prairie Research Institute, University of Illinois, Havana, IL 62644, USA
    Current affiliation:
    1. U.S. Geological Survey, South Dakota Cooperative Fish & Wildlife Research Unit, Department of Natural Resource Management, South Dakota State University, SD 57007, USA.
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  • Associate Editor: Terry Messmer

Abstract

Wetlands in the Upper Mississippi River and Great Lakes Region (UMRGLR) must annually sustain populations of migrating waterfowl from the mid-continent of North America. We used multi-stage sampling to estimate plant and invertebrate food biomasses (kg/ha) for ducks in 3 wetland habitat types at 6 stop-over locations in the UMRGLR during 2006 and 2007. Total biomass was greatest in palustrine emergent (PEM; equation image = 208 kg/ha, SE = 23, median = 120), followed by palustrine forested (PF; equation image = 87 kg/ha, SE = 7; median = 43), and lacustrine–riverine (LR; equation image = 52 kg/ha, SE = 7; median = 27) wetlands. Ducks that foraged in forested and LR wetlands encountered the least food abundance during spring in the UMRGLR. Our estimates of food abundance were the lowest reported among other landscape scale surveys from mid-continent North America. About 1 in every 5 PEM wetlands and over half of our PF and LR wetlands that we sampled contained <50 kg/ha of food, suggesting many had little or no forage value to ducks during spring. Biomass of plant foods generally exceeded invertebrate biomass in all habitat types, although invertebrate biomass estimates exceeded plant biomass in 8 of 29 sites when considered by wetland type and year. Total food biomass estimates varied widely (equation image = 6–425 kg/ha) between years and among habitats; thus, using global arithmetic means to estimate food abundance for conservation planning obscures fine scale temporal and spatial variation that may be necessary for management on local and sub-regional levels. Distributions of food biomass estimates were right-skewed, causing us to question whether arithmetic means realistically represent levels of food abundance that all ducks encounter during spring migration. Alternative measures of central tendency (e.g., median) may be more biologically realistic, particularly if spring-migrating ducks are not distributed in an ideal-free manner with respect to food abundance. Future research should determine how ducks distribute themselves in relation to variation in food abundance in space and time during spring migration to strengthen the biological approach to conservation planning in non-breeding Joint Venture areas of the North American Waterfowl Management Plan. © 2011 The Wildlife Society.

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