Timing of sea-ice retreat affects the distribution of seabirds and their prey in the southeastern Bering Sea

Abstract

§ 'Seabirds are like graduate students; they go where the food is.' Comment by Bob Paine on the occasion of an after-dinner talk on Seabirds as Feathered Oceanographers INTRODUCTION Marine ecosystems respond to climate forcing at a variety of temporal scales, from those of storm events, to periods of cooling and warming lasting millennia. While seasonal variability in heat and light is manifested in the ocean by changes in production and by migration of organisms to more favorable locations, changes in climate forcing lasting multiple years and longer may result in major reorganizations of food webs and ecosystem structure (e.g.

Seabird responses to a changing Bering Sea

“…In Hunt et al (2018), the at-sea distributions of both black-legged kittiwakes and common murres were centered on the inner shelf in cold years and shifted toward the middle shelf in warm years. These shifts may be comparable to those recorded for these 2 species by , who found in colonybased studies that these 2 species shift their foraging from basin waters to shelf waters in warm years.…”

“…In recent years with early sea-ice retreat, age-0 walleye pollock Gadus chalcogrammus have been abundant in the near-surface waters of the southeastern Bering Sea (e.g. Renner et al 2016, Hunt et al 2018). This availability of prey improved foraging conditions for the piscivorous black-legged kittiwakes Rissa tridactlya and thickbilled murres Uria lomvia breeding on the Pribilof Islands (Alaska, USA; Satterthwaite et al 2012.…”

“…Changes in the foraging distribution of red-legged kittiwakes during the breeding season were examined in 2 studies that used different approaches and time series, yet provided similar results. Hunt et al (2018), working with a 4-decade-long pelagic data set ( Fig. 1), found that red-legged kittiwakes made a fairly minor shift from deep basin waters to shallower waters in warm years.…”

“…These shifts may be comparable to those recorded for these 2 species by , who found in colonybased studies that these 2 species shift their foraging from basin waters to shelf waters in warm years. In warm years with early sea-ice retreat, middle and outer shelf waters have abundant age-0 walleye pollock in near-surface waters (Hunt et al 2018), and this source of prey was likely attractive to the 2 piscivorous bird species. Likewise, 3 contributions to this Theme Section found that the off-shelf-foraging thick-billed murres shifted their foraging to shelf Hunt et al (2018) obtained data on the pelagic distribution of seabirds.…”

“…There are 2 broad themes covered in this Theme Section. The first, examined by Hunt et al (2018), focuses on how the distribution and abundance of potential seabird prey are affected by climate variability via the timing of sea-ice retreat, and how these impacts on prey have affected the distributions of seabirds over the southeastern Bering Sea shelf since the mid-1970s. The second theme, addressed by colony-based studies relying on bird-borne data ABSTRACT: The eastern Bering Sea is well known for its spatial and temporal variability.…”