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Food resource availability for American black ducks wintering in southern New Jersey

Authors

  • Dane M. Cramer,

    1. Department of Entomology and Wildlife Ecology, University of Delaware, 249 Townsend Hall, Newark, DE 19716, USA
    Current affiliation:
    1. Ducks Unlimited, Inc., 1220 Eisenhower Place, Ann Arbor, MI 48108, USA.
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  • Paul M. Castelli,

    1. New Jersey Division of Fish and Wildlife, Nacote Creek Research Station, P.O. 418, Port Republic, NJ 08241, USA
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  • Tina Yerkes,

    1. Ducks Unlimited, Inc., 1220 Eisenhower Place, Ann Arbor, MI 48108, USA
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  • Christopher K. Williams

    Corresponding author
    1. Department of Entomology and Wildlife Ecology, University of Delaware, 253 Townsend Hall, Newark, DE 19716, USA
    • Department of Entomology and Wildlife Ecology, University of Delaware, 253 Townsend Hall, Newark, DE 19716, USA.
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  • Associate Editor: Michael Eichholz.

Abstract

Midwinter waterfowl survey data indicates a long-term decline in the number of wintering American black ducks (Anas rubripes), potentially due to habitat limitations. In order for future estimates of carrying capacity to be determined, it is critical that regional food availability is estimated. We collected pairs of habitat core samples (n = 510) from 5 habitat types in southern New Jersey, USA, during October, January, and April 2006–2008 to estimate resource availability and variability. We collected upper gastrointestinal tracts from hunter-killed birds (n = 45) and late season collections (n = 19) to identify food items and limited our estimates of resource availability to only winter food items; thereby reducing the availability of seed foods found in our core samples by 38% and animal foods by 96%. We did not detect differences in years or sampling period, but did between habitat types. Mudflat habitat had the greatest availability of invertebrate and vertebrate food items and appeared to supply the bulk of energy to black ducks wintering in southern New Jersey. We suggest conservation efforts to be focused on restoring or enhancing mudflat habitat as an integral component of an ecologically functioning salt marsh to increase food availability. © 2011 The Wildlife Society.

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