Asynchronous changes in phenology of migrating Broad-tailed Hummingbirds and their early-season nectar resources

Authors

  • Amy M. McKinney,

    Corresponding author
    1. Department of Biology, University of Maryland, College Park, Maryland 20742-4415 USA
    2. Rocky Mountain Biological Laboratory, P.O. Box 519, Crested Butte, Colorado 81224 USA
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  • Paul J. CaraDonna,

    1. Rocky Mountain Biological Laboratory, P.O. Box 519, Crested Butte, Colorado 81224 USA
    2. Department of Ecology and Evolutionary Biology, University of Arizona, Tucson, Arizona 85721 USA
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  • David W. Inouye,

    1. Department of Biology, University of Maryland, College Park, Maryland 20742-4415 USA
    2. Rocky Mountain Biological Laboratory, P.O. Box 519, Crested Butte, Colorado 81224 USA
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  • Billy Barr,

    1. Rocky Mountain Biological Laboratory, P.O. Box 519, Crested Butte, Colorado 81224 USA
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  • C. David Bertelsen,

    1. School of Natural Resources and the Environment, University of Arizona, Tucson, Arizona 85721 USA
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  • Nickolas M. Waser

    1. Rocky Mountain Biological Laboratory, P.O. Box 519, Crested Butte, Colorado 81224 USA
    2. Department of Ecology and Evolutionary Biology, University of Arizona, Tucson, Arizona 85721 USA
    3. School of Natural Resources and the Environment, University of Arizona, Tucson, Arizona 85721 USA
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  • Corresponding Editor: R. E. Irwin.

Abstract

Phenological advancements driven by climate change are especially pronounced at higher latitudes, so that migrants from lower latitudes may increasingly arrive at breeding grounds after the appearance of seasonal resources. To explore this possibility, we compared dates of first arrival of Broad-tailed Hummingbirds (Selasphorus platycercus) to dates of flowering of plants they visit for nectar. Near the southern limit of the breeding range, neither hummingbird arrival nor first flowering dates have changed significantly over the past few decades. At a nearby migration stopover site, first flowering of a major food plant has advanced, but peak flowering has not. Near the northern limit of the breeding range, first and peak flowering of early-season food plants have shifted to earlier dates, resulting in a shorter interval between appearance of first hummingbirds and first flowers. If phenological shifts continue at current rates, hummingbirds will eventually arrive at northern breeding grounds after flowering begins, which could reduce their nesting success. These results support the prediction that migratory species may experience the greatest phenological mismatches at the poleward limits of their migration. A novel hypothesis based on these results posits that the poleward limit for some species may contract toward lower latitudes under continued warming.

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