Proximate Cues for a Short-Distance Migratory Species: an Application of Survival Analysis

Authors

  • JED MEUNIER,

    Corresponding author
    1. Department of Wildlife Ecology, University of Wisconsin, 226 Russell Labs, 1630 Linden Drive, Madison, WI 53706, USA
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    • Department of Forest, Rangeland, and Watershed Stewardship, Colorado State University, Fort Collins, CO 80523, USA

  • RUI SONG,

    1. Department of Statistics, University of Wisconsin, B248 Medical Sciences Center, 1300 University Avenue, Madison, WI 53706, USA
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    • CB # 7420, McGavran-Greenberg Hall, School of Public Health, University of North Carolina, Chapel Hill, NC 27599, USA

  • R. SCOTT LUTZ,

    1. Department of Wildlife Ecology, University of Wisconsin, 226 Russell Labs, 1630 Linden Drive, Madison, WI 53706, USA
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  • DAVID E. ANDERSEN,

    1. United States Geological Survey, Minnesota Cooperative Fish and Wildlife Research Unit, Department of Fisheries, Wildlife, and Conservation Biology, University of Minnesota, St. Paul, MN 55108, USA
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  • KEVIN E. DOHERTY,

    1. Department of Fisheries, Wildlife, and Conservation Biology, Minnesota Cooperative Fish and Wildlife Research Unit, University of Minnesota, St. Paul, MN 55108, USA
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  • JOHN G. BRUGGINK,

    1. Department of Biology, Northern Michigan University, 1401 Presque Isle Avenue, Marquette, MI 49855, USA
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  • EILEEN OPPELT

    1. Department of Biology, Northern Michigan University, 1401 Presque Isle Avenue, Marquette, MI 49855, USA
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  • Department of Ecosystem and Conservation Sciences, College of Forestry and Conservation, University of Montana, Missoula, MT 59812, USA

jmeunier@lamar.colostate.edu

Abstract

ABSTRACT  Investigation of bird migration has often highlighted the importance of external factors in determining timing of migration. However, little distinction has been made between short- and long-distance migrants and between local and flight birds (passage migrants) in describing migration chronology. In addition, measures of food abundance as a proximate factor influencing timing of migration are lacking in studies of migration chronology. To address the relationship between environmental variables and timing of migration, we quantified the relative importance of proximate external factors on migration chronology of local American woodcock (Scolopax minor), a short distance migrant, using event-time analysis methods (survival analysis). We captured 1,094 woodcock local to our study sites in Michigan, Minnesota, and Wisconsin (USA) during autumn 2002–2004 and documented 786 departure dates for these birds. Photoperiod appeared to provide an initial proximate cue for timing of departure. Moon phase was important in modifying timing of departure, which may serve as a navigational aid in piloting and possibly orientation. Local synoptic weather variables also contributed to timing of departure by changing the rate of departure from our study sites. We found no evidence that food availability influenced timing of woodcock departure. Our results suggest that woodcock use a conservative photoperiod-controlled strategy with proximate modifiers for timing of migration rather than relying on abundance of their primary food, earthworms. Managing harvest pressure on local birds by adjusting season lengths may be an effective management tool with consistent migration patterns from year to year based on photoperiod.

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