Patterns of change in diets of two piscivorous seabird species during 35 years in the Pribilof Islands

Temporal shifts in seabird populations and spatial coherence with prey in the southeastern Bering Sea

“…In contrast, during fall the more dispersed distribution of seabirds over the middle SEBS shelf is consistent with observed distributions of several forage fish species throughout this region (ParkerStetter et al 2013). Capelin, for example, which historically was a larger component of seabird diets in the Bering Sea compared to recent decades (Sinclair et al 2008, Renner et al 2012, was only important in our models for shearwaters, which are omnivorous (Hunt et al 2002a, Baduini et al 2006, and surface piscivores (in fall only since we did not measure capelin abundance in summer). Capelin distribution exhibits high interannual variability, apparently mediated by ocean temperature (Ciannelli & Bailey 2005).…”

“…In fall, free from the constraint of central-place foraging and the energy demands of chick-rearing, seabirds are presumably able to be less selective and more omnivorous in their prey consumption. Our data and analyses of seabird prey in summer or fall, however, did not include some species such as squids (Gonatidae) and mesopelagic fishes (Myctophidae) that are known to be important prey for some seabird species or colonies in the Bering Sea (Sinclair et al 2008, Renner et al 2012.…”

“…Our study was part of the Bering Study and the Bering Sea Integrated Ecosystem Research Project (hereafter 'Bering Sea Project') that sought to understand mechanisms of physical forcing and climate effects on food availability, trophic relationships, and spatio-temporal variability in predatorprey dynamics in the Bering Sea (Harvey & Sigler 2013). The Bering Sea Project, along with prior ecosystem and long-term ecological studies, demonstrated that juvenile (age-0 to 1) walleye pollock Gadus chalcogrammus and euphaussiids (krill) were key prey items for seabirds in the SEBS in recent decades; however, capelin Mallotus villosus, sand lance Ammodytes hexapterus, and other prey also were regionally or historically important (Springer et al 1986, Sinclair et al 2008, Renner et al 2012, Harding et al 2013). Many seabird species in the Bering Sea are omnivorous, consuming different species of zooplankton and fishes, spatially between colonies or ecoregions, seasonally, and when self-feeding vs. provisioning chicks (Hunt et al 2002a, Paredes et al 2012, Renner et al 2012, Harding et al 2013.…”

“…The Bering Sea Project, along with prior ecosystem and long-term ecological studies, demonstrated that juvenile (age-0 to 1) walleye pollock Gadus chalcogrammus and euphaussiids (krill) were key prey items for seabirds in the SEBS in recent decades; however, capelin Mallotus villosus, sand lance Ammodytes hexapterus, and other prey also were regionally or historically important (Springer et al 1986, Sinclair et al 2008, Renner et al 2012, Harding et al 2013). Many seabird species in the Bering Sea are omnivorous, consuming different species of zooplankton and fishes, spatially between colonies or ecoregions, seasonally, and when self-feeding vs. provisioning chicks (Hunt et al 2002a, Paredes et al 2012, Renner et al 2012, Harding et al 2013. Abundance of these prey species can vary greatly by season, year, and region (Brodeur et al 1999, Hollowed et al 2012, Parker-Stetter et al 2013, Ressler et al 2014; for example, physical forcing from wind and winter sea ice extent over the shelf can greatly affect the distribution and abundance of fish populations in the SEBS (Hunt et al 2002b, Stabeno et al 2012a).…”

Does location really matter? An inter-colony comparison of seabirds breeding at varying distances from productive oceanographic features in the Bering Sea

“…Both the continental shelfbreak and the Aleutian shelf-break are characterized by elevated productivity, and provide important foraging grounds for seabirds in the Bering Sea Schneider, 1982;Springer et al, 1996). Although murre diets have been quantified at the three colonies (e.g., Iverson et al, 2007;Renner et al, 2012;Sinclair et al, 2008), very little is known about where murres from these colonies forage (Kokubun et al, 2008;Takahashi et al, 2008). Moreover, although there is evidence that Pribilof murres sometimes forage on the shelf, these data are restricted to very few years and the availability of shelf-based prey varies greatly among years (Sinclair et al, 2008).…”