Xantus's Murrelet Breeding Relative to Prey Abundance and Oceanographic Conditions in the Southern California Bight

Abstract

Many seabird studies have documented earlier breeding and higher reproductive success in years when prey is abundant (Cairns 1987, Croxall & Rothery 1991, Phillips et al. 1996). An increasing number of studies have focused on seabird responses to variability in oceanographic conditions (Ainley et al. 1995, Gaston & Smith 2001, Abraham & Sydeman 2004). Ocean productivity along the west coast of the United States is enhanced in the spring and summer by an influx of cool, nutrient-rich water from the north and localized upwelling that brings nutrients to the surface (Chelton et al. 1982, Schwing et al. 2000). Low sea-surface temperature (SST) and strong upwelling are, therefore, associated with high primary and secondary productivity in the region and can show substantial interannual variation (Chelton et al. 1982). Seabird studies have documented earlier breeding and higher reproductive success in years of stronger upwelling and lower SST, demonstrating the importance of “bottom-up” processes to higher trophic levels (Gaston & Smith 2001, Abraham & Sydeman 2004).