• Energy Research

Abstract Understanding storm impacts on marine vertebrate demography requires detailed meteorological data in tandem with long‐term population monitoring. Yet most studies use storm proxies such as the North Atlantic Oscillation Index (NAOI), potentially obfuscating a mechanistic understanding of current and future risk. Here, we investigate the impact of extratropical cyclones by extracting north Atlantic winter storm characteristics (storm number, intensity, clustering and wave conditions) and relating these with long‐term overwinter adult survival of three long‐lived sympatric seabirds which winter at sea—common guillemot Uria aalge, Atlantic puffin Fratercula arctica and razorbill Alca torda. We used multidecadal mark‐recapture analysis (1970s–2020s) to estimate survival while correcting for resighting probability, combined with spatially explicit environmental data from geolocation‐derived wintering areas, to determine the impact of different storm characteristics (i.e., number, intensity, duration, gap between storms, wave height and wind speed), as well as broad‐scale climatic conditions (NAOI and sea surface temperature [SST]). All three species experienced rapid population growth over the study period. Guillemot and razorbill survival was lower during stormier winters, with an additive effect of summer SST for guillemots, and a negative interaction with population size for razorbills. Puffin survival was negatively correlated with winter SST, and the lowest puffin survival coincided with intense winter storms and a large seabird wreck in 2013/14. The number of days with wind speed >30 and 35 ms−1 negatively impacted razorbill and guillemot survival, respectively, and puffin survival was higher when gaps between storms were longer. Our results suggest negative but divergent storm impacts on these closely related sympatric breeders, which may be compounded by warmer seas and density‐dependence as these populations return to their previously much larger sizes. We tentatively suggest that frequent, long‐lasting storms with strong winds are likely to have the greatest negative impact on auk survival. Moreover, we highlight the possibility of tipping points, where only the most extreme storms, that may become more frequent in the future, have measurable impacts on seabird survival, and no effect of NAOI.

AbstractIntroduced mammals have devastated island nesting seabird populations worldwide. Declines in breeding seabirds on St Kilda, UK, have been linked to climate change and predation from great skuasStercorarius skuas, but the introduced St Kilda field mouseApodemus sylvaticus hirtensismay also play a role by feeding on adults, chicks or eggs. Here, we use stable isotopes in St Kilda mouse blood and potential dietary items to investigate their foraging ecology, specifically focussing on the importance of seabirds and marine foods in their diet. Mice were seasonally sampled at three sites on Hirta, St Kilda over three consecutive years (2010–2012). The δ13C and δ15N ratios were used in analyses, including isotope niche and dietary source mixing models, to examine foraging behaviour among locations and between seabird breeding seasons. Mice sampled in Carn Mor – where the majority of the island’s seabirds nest - had consistently higher δ13C than other locations throughout the year, with δ15N also being significantly higher for all but one comparison. The isotopic niche width (SEAs) of Carn Mor mice in each season were distinct from the other locations, and became smaller during the seabird breeding season. Dietary mixing models revealed that seabirds made up a large proportion of the diet for mice from Carn Mor, particularly during the seabird breeding season. In conclusion, our work reveals that seabird-derived foods are likely to form a significant part of the diet of St Kilda mice populations located in and around breeding colonies. It is unclear however, whether this is from scavenging or predation of seabirds, or through their discarded food items. Given that mice have had significant effects on seabird populations elsewhere, it is important to carry out further work to determine whether mice are a significant cause of seabird mortality in this island ecosystem.

Climate change has had profound effects upon marine ecosystems, impacting across all trophic levels from plankton to apex predators. Determining the impacts of climate change on marine ecosystems requires understanding the direct effects on all trophic levels as well as indirect effects mediated by trophic coupling. The aim of this study was to investigate the effects of climate change on the pelagic food web in the Celtic Sea, a productive shelf region in the Northeast Atlantic. Using long-term data, we examined possible direct and indirect 'bottom-up' climate effects across four trophic levels: phytoplankton, zooplankton, mid-trophic level fish and seabirds. During the period 1986-2007, although there was no temporal trend in the North Atlantic Oscillation index (NAO), the decadal mean Sea Surface Temperature (SST) in the Celtic Sea increased by 0.66 +/- 0.02 degrees C. Despite this, there was only a weak signal of climate change in the Celtic Sea food web. Changes in plankton community structure were found, however this was not related to SST or NAO. A negative relationship occurred between herring abundance (0- and 1-group) and spring SST ( 0- group: p = 0.02, slope = -0.30560.125; 1-group: p = 0.04, slope = -0.410 +/- 0.193). Seabird demographics showed complex species-specific responses. There was evidence of direct effects of spring NAO ( on black-legged kittiwake population growth rate: p = 0.03, slope = 0.0314 +/- 0.014) as well as indirect bottom- up effects of lagged spring SST (on razorbill breeding success: p = 0.01, slope = -0.144 +/- 0.05). Negative relationships between breeding success and population growth rate of razorbills and common guillemots may be explained by interactions between mid-trophic level fish. Our findings show that the impacts of climate change on the Celtic Sea ecosystem is not as marked as in nearby regions (e.g. the North Sea), emphasizing the need for more research at regional scales.

Seabirds have a global distribution, are numerous throughout the world’s oceans, and have been used for decades to track and understand changes in the marine environment. They are dependent on a variety of ecosystems, including terrestrial, coastal, and pelagic, and are thus vulnerable to both marine and terrestrial environmental stressors. This chapter examines impacts on seabird populations that occur in the marine environment and are global in nature (touch more than one ocean basin). Both widespread (i.e., climate change induced alterations to marine food webs and sea level rise) and more point-source impacts (i.e., incidental bycatch in fisheries, hunting) are discussed. Additionally, natural occurrences in marine ecosystems (i.e., oceanographic regime shifts, parasites) and issues related to anthropogenic activities (i.e., plastic and oil pollution) are covered. Lastly, we discuss marine protected areas and other efforts aimed at conserving global seabird populations, including colony restoration, community-based research, and international conservation actions.

Abstract Interspecific competition can drive niche partitioning along multidimensional axes, including allochrony. Competitor matching will arise where the phenology of sympatric species with similar ecological requirements responds to climate change at different rates such that allochrony is reduced. Our study quantifies the degree of niche segregation in foraging areas and depths that arises from allochrony in sympatric Adélie and chinstrap penguins and explores its resilience to climate change. Three‐dimensional tracking data were sampled during all stages of the breeding season and were used to parameterise a behaviour‐based model that quantified spatial overlap of foraging areas under different scenarios of allochrony. The foraging ranges of the two species were similar within breeding stages, but differences in their foraging ranges between stages, combined with the observed allochrony of 28 days, resulted in them leapfrogging each other through the breeding season such that they were exploiting different foraging locations on the same calendar dates. Allochrony reduced spatial overlap in the peripheral utilisation distribution of the two species by 54.0% over the entire breeding season, compared to a scenario where the two species bred synchronously. Analysis of long‐term phenology data revealed that both species advanced their laying dates in relation to October air temperatures at the same rate, preserving allochrony and niche partitioning. However, if allochrony is reduced by just a single day, the spatial overlap of the core utilisation distribution increased by an average of 2.1% over the entire breeding season. Niche partitioning between the two species by allochrony appears to be resilient to climate change and so competitor matching cannot be implicated in the observed population declines of the two penguin species across the Western Antarctic Peninsula.