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Seabird parents during chick rearing is hypothesized to regulate body mass to reduce flight costs and invest energy in current reproduction. Alcids have 2â4 times higher wing-loading and higher flight costs than other seabirds. In particular, rhinoceros auklets Cerorhincamonocerata (RHAU) carry the heaviest meals among alcids despite its medium-size, therefore, we expected that they might be more likely to keep their body mass small and within a narrow range during chick rearing. We examined between-breeding stage and interannual variations in RHAU body mass using 27-year monitoring data, then tested whether the interannual variation shown by the coefficient of variation (CV) in body mass during chick rearing was smaller than in other seabirds, and if their body lipid stores were smaller. RHAU during chick rearing have 15â20 g lower body mass, corresponding to 5â7% decrease of flight costs, than those during incubation. We found that CV of body mass in RHAU (1.4) was smaller than those of 10 other seabird species (1.7â7.5), while CVs in provisioning metrics, such as meal mass, chick growth, fledgling mass, and fledging success, were the largest or second largest. RHAU body lipid stores during chick rearing (3.8â4.0%) was also smaller than six other species (5.7â9.5%). Results suggest that chick-rearing RHAU maintained a narrow range of body mass with minimum body lipid stores, possibly because of their greater wing-loading and heavier meals. Such constraints on body mass regulation might affect their variable investment in their chicks under environmental variability, as shown large variation in provisioning metrics., Author(s): Jumpei Okado [sup.1] [sup.2] , Yutaka Watanuki [sup.1] Author Affiliations: (1) grid.39158.36, 0000 0001 2173 7691, Graduate School of Fisheries Sciences, Hokkaido University, , 3-1-1 Minato-cho, Hakodate, 041â8611, Hokkaido, [...]

The North Pacific Transition Zone (NPTZ) is one of the most productive offshore regions. To identify important habitats for pelagic top predators within this region, we investigated the at-sea distributions of black-footed (Phoebastria nigripes) and Laysan albatrosses (P. immutabilis) by vessel-based surveys during their non-breeding season (July and October in 2010 and September and October in 2011). We developed statistical models using satellite-based oceanographic data at spatial scales of 4, 20 and 80 km to explain their densities. For both species, sea surface temperatures (SST) and distance to the Emperor Seamounts emerged as important factors in the better-fitting models at all spatial scales. In addition, black-footed albatrosses were widely distributed in the NPTZ (SST 17.7-27.4 °C), whereas Laysan albatrosses favoured northern and colder waters (13.6-25.4 °C). Our results also indicated that the Emperor Seamounts, where trawling and longline fishing occur, were an important habitat for both species in the NPTZ. Therefore, careful attention should be paid to interactions between fisheries and albatross species in this region. Electronic supplementary material The online version of this article (doi:10.1007/s00227-015-2620-1) contains supplementary material, which is available to authorized users., Author(s): Bungo Nishizawa[sup.1] , Daisuke Ochi[sup.2] , Hiroshi Minami[sup.2] , Kotaro Yokawa[sup.2] , Sei-Ichi Saitoh[sup.3] , Yutaka Watanuki[sup.1] Author Affiliations: (1) Graduate School of Fisheries Sciences, Hokkaido University, 3-1-1, Minato, [...]

The marine ecosystems of the Bering Sea and adjacent southern Chukchi Sea are experiencing rapid changes due to recent reductions in sea ice. Short-tailed shearwaters Puffinus tenuirostris visit this region in huge numbers between the boreal summer and autumn during non-breeding season, and represent one of the dominant top predators. To understand the implications for this species of ongoing environmental change in the Pacific subArctic and Arctic seas, we tracked the migratory movements of 19 and 24 birds in 2010 and 2011, respectively, using light-level geolocators. In both years, tracked birds occupied the western (Okhotsk Sea and Kuril Islands) and eastern (southeast Bering Sea) North Pacific from May to July. In August-September of 2010, but not 2011, a substantial proportion (68 % of the tracked individuals in 2010 compared to 38 % in 2011) moved through the Bering Strait to feed in the Chukchi Sea. Based on the correlation with oceanographic variables, the probability of shearwater occurrence was highest in waters with sea surface temperatures (SSTs) of 8-10°C over shallow depths. Furthermore, shearwaters spent more time flying when SST was warmer than 9°C, suggesting increased search effort for prey. We hypothesized that the northward shift in the distribution of shearwaters may have been related to temperature-driven changes in the abundance of their dominant prey, krill (Euphausiacea), as the timing of krill spawning coincides with the seasonal increase in water temperature. Our results indicate a flexible response of foraging birds to ongoing changes in the sub-Arctic and Arctic ecosystems., Introduction The Bering and southern Chukchi seas are among the most productive marine ecosystems in the world (Highsmith and Coyle 1990; Grebmeier 2012; Hunt et al. 2013). Reductions in sea [...]

Data from eight microsatellite markers screened in 246 rhinoceros auklets (Cerorhinca monocerata) from across the North Pacific revealed multiple genetic groups. The east (North America) to west (Japan) split was clearly evident in all analyses. Within the eastern Pacific, a minimum of three genetic groups are present. Surprisingly, rhinoceros auklets from Triangle Island, British Columbia, were genetically isolated from other nearby populations, including the breeding colony on Pine Island (~100 km to the east). A fourth genetic cluster (Chowiet Is) was detected using principal coordinate's analysis; however, sample sizes were limited. Patterns of differentiation correspond to nonbreeding distributions with the eastern and western Pacific birds spending time off the west coast of North America and Japan, respectively, and may represent historical isolation in separate refugia during the Pleistocene glaciations. The patterns of genetic structure result from a combination of historical and contemporary factors influencing dispersal of rhinoceros auklets., Introduction The rhinoceros auklet (Cerorhinca monocerata) breeds on islands in the North Pacific from California to Japan. Breeding colonies are not evenly distributed along the coastline nor are population numbers [...]

Mesopelagic myctophid fish are a key component of the world's ocean food webs, linking primary consumers and predators. Among marine predators, seabirds are globally significant consumers, but the extent to which they feed on myctophids has been investigated only at the regional scale. This global-scale review of analyses of the stomach contents of 228 seabird species reveals that the occurrence of myctophids in seabird diets is extremely variable. However, myctophids do constitute a considerable amount of the food of penguins, the Procellariidae (shearwaters/petrels, etc.), and storm-petrels; in locations where birds are foraging in oceanic basin/shelf slope habitat; and among birds that feed at night. Recent analyses of the fatty acid signature of stomach oil emphasize that myctophids can be important prey also for seabirds exploiting oceanic habitats. Current efforts to survey seabirds' distribution outside the breeding period, when they often become more oceanic, and their circadian activity may further support the global importance of myctophids as a pathway for carbon advection between marine compartments., Author(s): Yutaka Watanuki [sup.1] , Jean-Baptiste Thiebot [sup.2] Author Affiliations: (Aff1) 0000 0001 2173 7691, grid.39158.36, Graduate School of Fisheries Sciences, Hokkaido University, , Minato-cho 3-1-1, 041-8611, Hakodate, Japan (Aff2) [...]