Energetic considerations for managing double-crested cormorants on Lake Champlain |
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| Authors: | Adam E Duerr David E Capen Therese M Donovan |
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| Affiliation: | 1. School of Natural Resources and the Environment, University of Michigan, Ann Arbor, MI 48109, USA;2. Institute for Fisheries Research, School of Natural Resources and the Environment, University of Michigan, Ann Arbor, MI 48109, USA;3. NOAA-Great Lakes Environmental Research Laboratory, Ann Arbor, MI 48109, USA;4. Cooperative Institute for Limnology and Ecosystem Research, University of Michigan, Ann Arbor, MI 48109, USA;1. U.S. Environmental Protection Agency, Office of Research and Development, National Health and Environmental Effects Research Laboratory, Mid-Continent Ecology Division, 6201 Congdon Blvd., Duluth, MN 55804, USA;2. SRA International, Inc., 6201 Congdon Blvd., Duluth, MN 55804, USA;3. University of Minnesota Duluth, Natural Resources Research Institute, 5013 Miller Trunk Hwy., Duluth, MN 55811, USA;1. Department of Biological Sciences, University of Windsor, 401 Sunset Avenue, Windsor, ON N9B 3P4, Canada;2. Aquatic Research and Development Section, Ontario Ministry of Natural Resources, 320 Milo Road, Wheatley, ON N0P2P0, Canada;3. Fairport Fish Research Station, Ohio Department of Natural Resources, 1190 High St., Fairport Harbor, OH 44077, USA;1. University of Waterloo, 200 University Avenue W., Waterloo, Ontario N2L 3G1, Canada;2. Ontario Ministry of the Environment, 125 Resources Road, Toronto, Ontario M9P 3V6, Canada;3. Bruce Power, P.O. Box 1540, Tiverton, Ontario, Canada |
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| Abstract: | We studied foraging distribution, activity budgets, fish consumption, and energetics of double-crested cormorants (Phalacrocorax auritus) at two breeding colonies on Lake Champlain. Our objective was to determine if fish consumption and distribution of predation changed with movements of cormorants associated with efforts to reduce numbers of cormorants on one of the colonies. Wildlife managers reduced populations of cormorants on Young Island, Vermont by oiling their eggs, which resulted in dispersal of breeding cormorants 35 km south to Four Brothers Islands, New York. We found that as cormorants shifted from Young Island to the colony on Four Brothers Islands, energy demands, foraging distribution, and total fish consumption increased. Birds on Four Brothers Islands foraged a greater distance from the colony compared to birds on Young Island. Additionally, consumption of yellow perch (Perca flavescens) shifted to rainbow smelt (Osmerus mordax) when more birds bred on Four Brothers Islands. The dispersal of cormorants from Young Island to Four Brothers Islands reduced predation on yellow perch but increased overall fish consumption. Our estimates of fish consumption ranged from 322,000–425,000 kg of fish per year at Young Island to 899,000–1,086,000 kg of fish per year at Four Brothers Islands. Results from this study demonstrate secondary impacts of management on Young Island to unmanaged areas. |
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