Range-wide reproductive consequences of ocean climate variability for the seabird Cassin's Auklet

Authors

  • Shaye G. Wolf,

    1. Department of Ecology and Evolutionary Biology, University of California, Center for Ocean Health, 100 Shaffer Road, Santa Cruz, California 95060 USA
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    •  Present address: Center for Biological Diversity, 351 California Street, Suite 600, San Francisco, California 94104 USA. E-mail: swolf@biologicaldiversity.org

  • William J. Sydeman,

    1. Point Reyes Bird Observatory Conservation Science, Marine Ecology Division, 3820 Cypress Drive #11, Petaluma, California 94954 USA
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    •  Present address: Farallon Institute for Advanced Ecosystem Research, P.O. Box 750756, Petaluma, California 94975 USA.

  • J. Mark Hipfner,

    1. Canadian Wildlife Service, Pacific Wildlife Research Centre, RR #1, 5421 Robertson Road, Delta, British Columbia V4K 3N2 Canada
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  • Christine L. Abraham,

    1. Point Reyes Bird Observatory Conservation Science, Marine Ecology Division, 3820 Cypress Drive #11, Petaluma, California 94954 USA
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  • Bernie R. Tershy,

    1. Department of Ecology and Evolutionary Biology, University of California, Center for Ocean Health, 100 Shaffer Road, Santa Cruz, California 95060 USA
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  • Donald A. Croll

    1. Department of Ecology and Evolutionary Biology, University of California, Center for Ocean Health, 100 Shaffer Road, Santa Cruz, California 95060 USA
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Abstract

We examine how ocean climate variability influences the reproductive phenology and demography of the seabird Cassin's Auklet (Ptychoramphus aleuticus) across ∼2500 km of its breeding range in the oceanographically dynamic California Current System along the west coast of North America. Specifically, we determine the extent to which ocean climate conditions and Cassin's Auklet timing of breeding and breeding success covary across populations in British Columbia, central California, and northern Mexico over six years (2000–2005) and test whether auklet timing of breeding and breeding success are similarly related to local and large-scale ocean climate indices across populations. Local ocean foraging environments ranged from seasonally variable, high-productivity environments in the north to aseasonal, low-productivity environments to the south, but covaried similarly due to the synchronizing effects of large-scale climate processes. Auklet timing of breeding in the southern population did not covary with populations to the north and was not significantly related to local oceanographic conditions, in contrast to northern populations, where timing of breeding appears to be influenced by oceanographic cues that signal peaks in prey availability. Annual breeding success covaried similarly across populations and was consistently related to local ocean climate conditions across this system. Overall, local ocean climate indices, particularly sea surface height, better explained timing of breeding and breeding success than a large-scale climate index by better representing heterogeneity in physical processes important to auklets and their prey. The significant, consistent relationships we detected between Cassin's Auklet breeding success and ocean climate conditions across widely spaced populations indicate that Cassin's Auklets are susceptible to climate change across the California Current System, especially by the strengthening of climate processes that synchronize oceanographic conditions. Auklet populations in the northern and central regions of this ecosystem may be more sensitive to changes in the timing and variability of ocean climate conditions since they appear to time breeding to take advantage of seasonal productivity peaks.

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