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Marine Ecology Progress Series

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MEPS 393:211-223 (2009)  -  DOI:

Winter pre-conditioning of seabird phenology in the California Current

Isaac D. Schroeder1,*, William J. Sydeman2,3, Nandita Sarkar1, Sarah Ann Thompson2, Steven J. Bograd1, Franklin B. Schwing1

1NOAA, Southwest Fisheries Science Center, Environmental Research Division, 1352 Lighthouse Avenue, Pacific Grove, California 93950-2097, USA
2Farallon Institute for Advanced Ecosystem Research, PO Box 750756, Petaluma, California 94954, USA
3Bodega Marine Laboratory, 2099 Westside Road, Bodega Bay, California 94923, USA

ABSTRACT: Climate change is predicted to affect the phasing and amplitude of upwelling in eastern boundary current marine ecosystems. Effects may be strongest during the spring or summer ‘upwelling season,’ but may also be influential during winter before the spring transition. We tested the hypothesis that wintertime environmental forcing ‘pre-conditions’ the ecosystem and affects the timing and success of breeding in 2 species of seabird, Cassin’s auklet Ptychoramphus aleuticus and common murre Uria aalge, reproducing in the central California Current. Time series of the mean and variance of egg-laying dates were correlated with regional winds and sea surface temperature, which were used as proxies for the forcing and oceanic response of coastal upwelling, respectively. Winter proxies of upwelling were the most significant determinants of seabird reproductive phenology, with anomalously strong upwelling in January to March leading to earlier dates of egg-laying in both species. We hypothesized that anomalous (early) winter upwelling, even of weak magnitude or short duration, could seed the region with sufficient nutrients to enhance productivity and prey availability, leading to a healthier adult breeding population and an earlier start to the breeding season. The magnitude of the previous year’s November winds were also positively correlated with the variance of egg-laying dates for the common murre, with upwelling-favorable winds leading to greater synchrony in egg-laying. We conclude that winter environmental conditions are important determinants of ecosystem dynamics in the California Current, and that seabird phenology is a particularly useful ecosystem indicator.

KEY WORDS: Cassin’s auklet · Common murre · California current · Phenology · Upwelling · Winter · Ecosystem indicator

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Cite this article as: Schroeder ID, Sydeman WJ, Sarkar N, Thompson SA, Bograd SJ, Schwing FB (2009) Winter pre-conditioning of seabird phenology in the California Current. Mar Ecol Prog Ser 393:211-223.

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