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Foraging niche specialization is thought to occur when different members of speciose communities divide resources in either time or space. Here we compared habitat preferences of the congeneric Grey Petrel Procellaria cinerea and White‐chinned Petrel Procellaria aequinoctialis, tracked in the same calendar year using GPS loggers from Gough Island and Bird Island (South Georgia), respectively. We identified periods of active foraging and determined habitat characteristics using remote‐sensing data. Although these highly pelagic species could potentially overlap at sea across large areas, they showed markedly different foraging preferences during their incubation periods, which are temporally offset because Grey Petrels breed during the austral winter. Grey Petrels foraged mostly in pelagic cold‐water areas to the north‐west of South Georgia, whereas White‐chinned Petrels foraged almost exclusively in the warm, shallow waters of the Patagonian Shelf. Within each species, foraging habitat characteristics were highly consistent. Our results demonstrate the diversity of habitat preferences within genera, and provide further evidence that colony‐specific information on habitat preference is crucial to identify important feeding areas for pelagic predators. [ABSTRACT FROM AUTHOR]

The use of miniaturized electronic tracking devices has illuminated our understanding of seabird distributions and habitat use, and how anthropogenic threats interact with seabirds in both space and time. To determine the year‐round distribution of adult Campbell albatross (Thalassarche impavida), a single‐island endemic, breeding only at Campbell Island in New Zealand's subantarctic, a total of 68 year‐long location data sets were acquired from light‐based geolocation data‐logging tags deployed on breeding birds in 2009 and 2010.During the incubation and chick‐guard phases of the breeding season, birds used cool (<10°C) waters over the Campbell Plateau, but also ranged over deeper, shelf‐break and oceanic waters (4,000–5,500 m) beyond the Plateau. Later in the breeding season, during post‐guard chick‐rearing, Campbell albatrosses exploited generally deep waters (4,000–5,000 m) beyond the Campbell Plateau.During the non‐breeding period, adults tended to move northwards into warmer (approximately 15°C) waters and occupied areas beyond western Australia in the west to offshore from Chile in the east. Overall, about 30% of adults spent some of their non‐breeding period in the central and eastern Pacific Ocean, substantially expanding the previously reported range for this species.One bird, that failed in its breeding attempt in October 2009, departed Campbell Island and circumnavigated the southern oceans before being recaptured back at Campbell Island in October 2010. This is the first example of an annually‐breeding albatross species completing a circumnavigation between breeding attempts.Overlap with fishing effort, using data from the Global Fishing Watch database, was assessed on a monthly and seasonal basis. Generally, levels of overlap between Campbell albatross and fishing effort were relatively low during the breeding season but were approximately 60% higher during the non‐breeding period, underlining the need for international initiatives to safeguard this species. [ABSTRACT FROM AUTHOR]

The Southern Ocean represents a continuous stretch of circumpolar marine habitat, but the potential physical and ecological drivers of evolutionary genetic differentiation across this vast ecosystem remain unclear. We tested for genetic structure across the full circumpolar range of the white‐chinned petrel (Procellaria aequinoctialis) to unravel the potential drivers of population differentiation and test alternative population differentiation hypotheses. Following range‐wide comprehensive sampling, we applied genomic (genotyping‐by‐sequencing or GBS; 60,709 loci) and standard mitochondrial‐marker approaches (cytochrome b and first domain of control region) to quantify genetic diversity within and among island populations, test for isolation by distance, and quantify the number of genetic clusters using neutral and outlier (non‐neutral) loci. Our results supported the multi‐region hypothesis, with a range of analyses showing clear three‐region genetic population structure, split by ocean basin, within two evolutionary units. The most significant differentiation between these regions confirmed previous work distinguishing New Zealand and nominate subspecies. Although there was little evidence of structure within the island groups of the Indian or Atlantic oceans, a small set of highly‐discriminatory outlier loci could assign petrels to ocean basin and potentially to island group, though the latter needs further verification. Genomic data hold the key to revealing substantial regional genetic structure within wide‐ranging circumpolar species previously assumed to be panmictic. [ABSTRACT FROM AUTHOR]

Speciation through homoploid hybridization (HHS) is considered extremely rare in animals. This is mainly because the establishment of reproductive isolation as a product of hybridization is uncommon. Additionally, many traits are underpinned by polygeny and/or incomplete dominance, where the hybrid phenotype is an additive blend of parental characteristics. Phenotypically intermediate hybrids are usually at a fitness disadvantage compared with parental species and tend to vanish through backcrossing with parental population(s). It is therefore unknown whether the additive nature of hybrid traits in itself could lead successfully to HHS. Using a multi-marker genetic data set and a meta-analysis of diet and morphology, we investigated a potential case of HHS in the prions (Pachyptila spp.), seabirds distinguished by their bills, prey choice, and timing of breeding. Using approximate Bayesian computation, we show that the medium-billed Salvin's prion (Pachyptila salvini) could be a hybrid between the narrow-billed Antarctic prion (Pachyptila desolata) and broad-billed prion (Pachyptila vittata). Remarkably, P. salvini' s intermediate bill width has given it a feeding advantage with respect to the other Pachyptila species, allowing it to consume a broader range of prey, potentially increasing its fitness. Available metadata showed that P. salvini is also intermediate in breeding phenology and, with no overlap in breeding times, it is effectively reproductively isolated from either parental species through allochrony. These results provide evidence for a case of HHS in nature, and show for the first time that additivity of divergent parental traits alone can lead directly to increased hybrid fitness and reproductive isolation. [ABSTRACT FROM AUTHOR]

Gelatinous zooplankton are a large component of the animal biomass in all marine environments, but are considered to be uncommon in the diet of most marine top predators. However, the diets of key predator groups like seabirds have conventionally been assessed from stomach content analyses, which cannot detect most gelatinous prey. As marine top predators are used to identify changes in the overall species composition of marine ecosystems, such biases in dietary assessment may impact our detection of important ecosystem regime shifts. We investigated albatross diet using DNA metabarcoding of scats to assess the prevalence of gelatinous zooplankton consumption by two albatross species, one of which is used as an indicator species for ecosystem monitoring. Black-browed and Campbell albatross scats were collected from eight breeding colonies covering the circumpolar range of these birds over two consecutive breeding seasons. Fish was the main dietary item at most sites; however, cnidarian DNA, primarily from scyphozoan jellyfish, was present in 42% of samples overall and up to 80% of samples at some sites. Jellyfish was detected during all breeding stages and consumed by adults and chicks. Trawl fishery catches of jellyfish near the Falkland Islands indicate a similar frequency of jellyfish occurrence in albatross diets in years of high and low jellyfish availability, suggesting jellyfish consumption may be selective rather than opportunistic. Warmer oceans and overfishing of finfish are predicted to favour jellyfish population increases, and we demonstrate here that dietary DNA metabarcoding enables measurements of the contribution of gelatinous zooplankton to the diet of marine predators. [ABSTRACT FROM AUTHOR]

Assessing broad-scale changes in seabird populations across the North Atlantic requires an integration of available datasets to understand the spatial extent of potential drivers and demographic change. Here, we compared survival of Northern Fulmars Fulmarus glacialis from a Scottish and an Irish colony from 1974 to 2009. Despite lower recapture probabilities of monel-ringed Irish birds compared with colour-ringed Scottish birds, survival probability decreased at both colonies. The extent to which the decline in survival is related to density-dependent processes or other external drivers remains uncertain, but our results suggest that these changes in survival are possibly indicative of larger-scale processes and are not confined to local colony dynamics. [ABSTRACT FROM AUTHOR]

Aim Species that breed sympatrically often occupy different foraging niches to mitigate competition for prey. When resource availability declines at the end of the breeding season, some animals migrate to regions with more favourable environmental conditions. When these life-history traits combine, foraging habitat preferences may continue to influence migration patterns and habitat utilization. The Bering Sea is home to the red-legged kittiwake ( RLKI), Rissa brevirostris, which is endemic, and the black-legged kittiwake ( BLKI), Rissa tridactyla, which has a circumpolar breeding distribution. Since the 1970s, numbers of RLKIs at the largest colony have declined and then recovered, whilst the BLKI population has remained stable. Knowledge of the migration ecology of kittiwakes is key to understanding differences in population trajectories, and predicting possible future responses of these species to climate change. Location Pribilof Islands, Bering Sea, subarctic North Pacific. Methods Using geolocation loggers, we tracked adult RLKIs and BLKIs during their non-breeding migrations. We used iterative methods to assess suitable sample sizes for determining space use. Kittiwakes are surface foragers; therefore we used wet-dry data to distinguish active foraging behaviour and to test the species' responses to environmental conditions. Stable isotope ratios of feathers grown during the non-breeding period were used to assess dietary niche. Results RLKIs remained largely in the Bering Sea, where they experienced colder conditions and shorter days; individual birds used multiple habitats, including the continental shelves, the sea-ice edge and pelagic waters. In contrast, BLKIs migrated to the subarctic North Pacific, where they dispersed laterally across the basin; the majority of birds travelled to the western subarctic. RLKIs spent less time actively foraging than BLKIs, and consumed higher trophic-level prey. Main conclusions The disparate wintering ranges and foraging behaviour of BLKIs and RLKIs suggest distinct environmental factors drive variation in overwinter survival. A strong association with sea ice, and specialization both in diet and foraging behaviour, may make RLKIs particularly vulnerable to climatic change. [ABSTRACT FROM AUTHOR]

Interspecific competitive interactions typically result in niche differentiation to alleviate competition through mechanisms including character displacement. However, competition is not the sole constraint on resource partitioning, and its effects are mediated by factors including the environmental context in which species coexist., Colonial seabirds provide an excellent opportunity to investigate the importance of competition in shaping realized niche widths because their life histories lead to variation in intra- and interspecific competition across the annual cycle. Dense breeding aggregations result in intense competition for prey in surrounding waters, whereas non-breeding dispersal to larger geographical areas produces lower densities of competitors., Bayesian hierarchical models of the isotopic niche, closely aligned to the trophic niche, reveal the degree of segregation between species and functional groups during both time periods. Surprisingly, species explained far more of the variance in the isotopic niche during the non-breeding than the breeding period., Our results underline the key role of non-breeding dynamics in alleviating competition and promoting distinctions between species through the facilitation of resource partitioning. Such situations may be common in a diverse range of communities sustained by ephemeral but abundant food items., This highlights how consideration of the hierarchical grouping of competitive interactions alongside consideration of abiotic constraints across the complete annual cycle allows a full understanding of the role of competition in driving patterns of character displacement. [ABSTRACT FROM AUTHOR]

Antarctic marine ecosystems are often considered to be pristine environments, yet wildlife in the polar regions may still be exposed to high levels of environmental contaminants. Here, we measured total mercury (THg) concentrations in blood samples from adult brown skuas Stercorarius antarcticus lonnbergi (n = 82) from three breeding colonies south of the Antarctic Polar Front in the Southern Ocean (southwest Atlantic region): (i) Bahía Esperanza/Hope Bay, Antarctic Peninsula; (ii) Signy Island, South Orkney Islands; and, (iii) Bird Island, South Georgia. Blood THg concentrations increased from the Antarctic Peninsula towards the Antarctic Polar Front, such that Hg contamination was lowest at Bahía Esperanza/Hope Bay (mean ± SD, 0.95 ± 0.45 μg g−1 dw), intermediate at Signy Island (3.42 ± 2.29 μg g−1 dw) and highest at Bird Island (4.47 ± 1.10 μg g−1 dw). Blood THg concentrations also showed a weak positive correlation with δ15N values, likely reflecting the biomagnification process. Males had higher Hg burdens than females, which may reflect deposition of Hg into eggs by females or potentially differences in their trophic ecology. These data provide important insights into intraspecific variation in contamination and the geographic transfer of Hg to seabirds in the Southern Ocean. [Display omitted] • Blood total mercury (THg) concentrations were measured in skuas across a latitudinal gradient. • Hg contamination increased from the Antarctic Peninsula to South Georgia. • Blood THg concentrations showed a weak positive correlation with δ15N. • Male brown skuas showed higher Hg contamination than females. [ABSTRACT FROM AUTHOR]

Aim Extensive development of human activities in combination with ocean warming is rapidly modifying marine habitats in the Arctic and North Atlantic regions. To understand the potential impacts on marine biodiversity, there is an urgent need to determine distributions and habitat preferences of potentially vulnerable species and to identify sensitive hotspots that might require particular protection. Our aims were to track one of the most abundant seabirds of the world, the little auk ( Alle alle), to provide a large, meta-population scale overview of its non-breeding distribution and to document potential threats to this species from human activities and other environmental changes. Location Arctic North Atlantic. Methods Using light-level geolocators, we investigated the 2010/11 non-breeding distribution of 65 little auks from four major colonies distributed throughout the Arctic North Atlantic. Bird distribution during the moulting, wintering and pre-breeding periods was compared with (1) the extent of the marginal ice zone and (2) the areas covered by the main shipping lanes and oil and gas activity licences. Results We identify several hotspots for this species, including two key areas located in the Greenland Sea and off Newfoundland. Crucially, we show that some of these hotspots overlap extensively with areas of intensive human activities, including oil and gas extraction and shipping. As little auks, which spend the major part of their time on the sea surface, are extremely vulnerable to marine pollution, our results emphasize the risk associated with the projected expansion of these activities. Main conclusions We conclude that management of further human enterprises in the Arctic needs to be based on more thorough risk assessment, requiring a substantial improvement in our knowledge of the distribution of sensitive species. [ABSTRACT FROM AUTHOR]

The processes driving age-related variation in demographic rates are central to understanding population and evolutionary ecology. An increasing number of studies in wild vertebrates find evidence for improvements in reproductive performance traits in early adulthood, followed by senescent declines in later life. However, life history theory predicts that reproductive investment should increase with age as future survival prospects diminish, and that raised reproductive investment may have associated survival costs. These non-mutually exclusive processes both predict an increase in breeding performance at the terminal breeding attempt. Here, we use a 30-year study of wandering albatrosses ( Diomedea exulans) to disentangle the processes underpinning age-related variation in reproduction. Whilst highlighting the importance of breeding experience, we reveal senescent declines in performance are followed by a striking increase in breeding success and a key parental investment trait at the final breeding attempt. [ABSTRACT FROM AUTHOR]

Individual foraging site fidelity, whereby individuals repeatedly visit the same foraging areas, is widespread in nature, and likely benefits individuals through higher foraging efficiency and potentially, higher breeding success. It may arise as a consequence of habitat or resource specialisation, or alternatively, where resources are abundant or predictable, the partitioning of space might guarantee individuals exclusive foraging opportunities. We tracked seven adult great black‐backed gulls Larus marinus at a North Sea colony from early incubation to the end of the breeding season in 2016, providing a total of 1170 foraging trips over a mean ± SD tracking period of 67 ± 16 days. There was clear spatial segregation between individuals, with almost no overlap of their core areas (50% utilisation distribution) during incubation and chick‐rearing. Core areas were relatively small and there was high repeatability (R ± SE) in foraging parameters, including initial departure direction (0.73 ± 0.11), foraging range (0.41 ± 0.14) and cumulative distance travelled (0.19 ± 0.1) throughout the breeding season. Despite the low spatial overlap, there was little evidence of differential habitat use by individuals. The near‐exclusive individual foraging areas of this species, usually considered to be a generalist, indicate that where there is high resource availability throughout the breeding season and a small local population, individuals appear to adopt a territorial strategy which likely reduces intraspecific competition. [ABSTRACT FROM AUTHOR]

Tracking of seabirds at sea is valuable for marine spatial planning. Many seabirds are of conservation concern, including albatrosses and large petrels (Procellariiformes) which face a major threat from mortality in fisheries. We examine how important areas used by seven of these species breeding at South Georgia change throughout the year, based on tracking data collected between 1991 and 2012, and discuss the implications for spatial management in the region within the current jurisdictional framework. Foraging areas overlapped with a patchwork of national and international management organizations, and areas outside clear jurisdiction. National waters were generally unimportant, besides that of South Georgia. The other exception was Falkland Islands coastal waters, which were important for wandering albatrosses Diomedea exulans during incubation, and were opened for new oil and gas drilling in 2015. The marine protected area established at the South Orkney Islands protects very little habitat used by the tracked seabirds; however, a northern extension of this would benefit a number of species at different breeding stages. The area around South Georgia was important year-round, including in periods when fishing is allowed. A contiguous region to the north of this was also important and here, mechanisms should be improved to ensure compliance with bird bycatch mitigation recommendations. The study highlighted the use of tracking for identifying key areas for pelagic albatrosses and petrels, and the advantages of incorporating these data into a multilateral approach to marine spatial planning to ensure the future conservation of these highly-threatened marine predators. [ABSTRACT FROM AUTHOR]

Two hypotheses have been proposed to explain sex-related differences in foraging in sexually monomorphic seabirds. The ‘intersexual competition’ hypothesis suggests that parents are in competition and that the dominated sex must adapt its behaviour to avoid competing with the dominant one. The ‘energetic constraint’ hypothesis suggests that differential energetic requirements lead to different foraging behaviour. We examined sexual differences in foraging behaviour of a sexually monomorphic tropical seabird, the Barau’s petrel, Pterodroma baraui, throughout the breeding period. We found sexual differences in foraging habitats and activities, but these were not consistent throughout the breeding period. During the prelaying exodus, males foraged further from the colony, in waters with greater surface chlorophyll concentration, and were more active than females. Males systematically took the first incubation shift, which was always longer than the others. However, no sex-related differences in foraging behaviour were observed during the chick-rearing period, both sexes sharing parental duties equally. We suggest that the sexual differences observed early in the breeding period are due to the specific needs of males and females. Females need to restore their body condition as quickly as possible after laying, which forces males to take the first long incubation shift at the nest. This may explain why males forage more actively during the prelaying exodus, to prepare for this long fasting period. Our results support for the first time the ‘energy constraint’ hypothesis to explain sexual differences in behaviour of a small, monomorphic procellariiform seabird. [Copyright &y& Elsevier]

Several species of seabirds show cyclic patterns of attendance at their nesting colonies. We examined the patterns of variation in the numbers of Cory''s shearwater at three colonies (two oceanic and one located on the continental shelf), including the world''s largest, at Selvagem Grande, Madeira, Portugal and considered several hypotheses concerning their causal mechanisms. At Selvagem Grande, cycles were exceptionally marked and regular, with a periodicity ranging from 7.8 to 11 days, and involved both breeders and nonbreeders. In contrast, variation in numbers was aperiodic at a nearby and much smaller colony (Selvagem Pequena), and also at the colony located off the Portuguese coast (Berlenga Island). We found no relationships between number of birds ashore and environmental variables such as wind direction and speed or lunar cycle. Cycles did not seem to be driven by oscillations in food availability or accessibility, given that they did not correlate with daily chick growth rates (which were acyclic) or diet. Despite their regularity, cycles were slightly out of phase in different sectors of Selvagem Grande, which suggests that social interactions at the colony could act as an entrainment agent for an endogenous rhythm, and so cycles are probably more likely to occur in large and dense colonies. Observations are consistent with the hypothesis that cycles facilitate social interactions by maximizing the probability of encounters at the colony. However, the exact mechanisms through which these remarkable cycles are controlled are still completely unknown, and clearly further research is needed. [Copyright &y& Elsevier]