Reproductive success of planktivorous seabirds in the North Pacific is related to ocean climate on decadal scales

Growing evidence indicates relationships between seabird demography and both largeand small-scale variation in climate and oceanography, yet few studies have examined multiple species and locations simultaneously. As secondary consumers, least, whiskered, and crested auklets (Aethia pusilla, A. pygmaea, and A. cristatella, respectively), congeneric planktivorous seabirds endemic to the Bering and Okhotsk seas, are expected to respond to changes in ocean climate due to their low trophic positioning. From 1990 to 2008, we measured reproductive success (productivity) and breeding phenology (mean hatching date) of auklets on Buldir, Kiska, and Kasatochi, 3 islands spanning 585 km across the Aleutian Islands, Alaska, USA. A model including Island, Species, and Winter Aleutian Low Pressure Index (ALPI) best explained productivity, with reproductive success decreasing among all species with increasing ALPI (β = -0.273 ± 0.0263 [SE]), likely through control of water temperature and prey (zooplankton) availability. Auklet productivity also increased with increasing winter sea surface temperature (SST) in the western North Pacific and western Bering Sea (and correspondingly decreased with increasing SST in the Gulf of Alaska), and was correlated negatively with spring sea-level air pressure in the North Pacific. These responses are reflective of positive values of the Aleutian low pressure system. Though our datasets cover only 19 yr or less, we found similar correlations between climate and auklet productivity among all species and islands. Together, our results suggest that ocean climatic conditions and reproductive success of planktivorous auklets are significantly related.