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Morphological variation in biological structures may be driven by genetic and environmental factors, such as inter- and intraspecific competition for resources. In seabirds, although the bill is also involved in vocalization, olfaction, sexual selection and defence, the main drivers of high morphological plasticity in bill size and shape appear to relate primarily to diet and thus to niche differentiation. Here, we combined geometric morphometrics and comparisons of linear measurements as a precise tool for measuring shape variation in anatomical features, to investigate the differences among species and populations (island groups) in bill shape of three planktivorous petrels (Antarctic prion Pachyptila desolata, blue petrel Halobaena caerulea and thin-billed prion Pachyptila belcheri). Fieldwork was carried out in South Georgia (54° 0' S, 38° 3' W), Falkland (51° 42' S, 57° 51' W), Diego Ramírez (56° 31' S, 68° 44' W) and Kerguelen (49° 20' S, 69° 20' E) Islands, from 2010 to 2021. Results show that the bills of Antarctic prions were more robust and shorter, appropriate for filtering large amounts of small prey. Blue petrels and thin-billed prions had narrower and longer bills, effective for catching and tearing large single prey. Also, Antarctic prions and blue petrels from Kerguelen had longer and narrower bills than conspecifics from other colonies, which could potentially be explained by geographic variation in diet. In conclusion, prey availability and diversity appear to be important factors influencing variation in bill morphology. This study highlights the utility of geometric morphometrics for investigating bill shape variation in seabirds. Nevertheless, further studies are needed to better understand selective pressures leading to morphological variation of biological structures., Author(s): Maria I. Laranjeiro [sup.1] [sup.2] , Marc Farré [sup.1] [sup.3] , Richard A. Phillips [sup.4] , Petra Quillfeldt [sup.5] , Francesco Bonadonna [sup.6] , Charlene Gémard [sup.6] , Maximiliano [...]

Stable isotope ratios of carbon (δ13C) and nitrogen (δ15N) were measured in feathers to compare the non-breeding distributions and habitat use of adult brown skuas Stercorarius antarcticus lönnbergi from high-latitude colonies at Esperanza/Hope Bay (Antarctic Peninsula, 63°S) and Signy Island (South Orkneys, 60°S), with those from Bird Island (South Georgia, 54°S), which have also been tracked previously using geolocators. Breeding colony, but not sex, had a significant effect on feather δ13C and δ15N values. Feather stable isotope data from South Georgia birds mostly corresponded to oceanic, mixed subtropical–subantarctic to subantarctic waters, which agrees with the tracking data, as did a subset of the birds from the two higher latitude populations. However, other individuals displayed feather stable isotope ratios that were consistent with continental shelf or shelf-slope waters, suggesting that unlike the vast majority of brown skuas from South Georgia, many birds from higher latitude colonies spend the non-breeding season on, or near, the Patagonian Shelf. These population-level differences may have implications for exposure to anthropogenic threats or have carryover effects on subsequent breeding behaviour or performance. [ABSTRACT FROM AUTHOR]

Northern Macronectes halli and southern giant petrels M. giganteus are opportunistic predators and the dominant avian scavengers in sub-Antarctic and Antarctic ecosystems. At South Georgia, there are globally important breeding populations of both species; however, no detailed diet study has been carried out at this site for > 35 years. Here, we analysed stomach contents of northern (n = 81) and southern giant petrel (n = 73) chicks at Bird Island, South Georgia (2014/15-2016/17). Specifically, we investigated: (1) interspecific and sexual dietary segregation; (2) diet changes within and among recent years; and (3) long-term diet changes since 1979/80-1980/81. Overall diet composition was similar between species, with penguins comprising approximately half the diet by mass. In both species (but more pronounced in southern giant petrels), prey delivered by female parents included higher proportions (by mass) of penguins and Antarctic krill Euphausia superba, and by male parents included more Antarctic fur seal Arctocephalus gazella carrion and seabirds other than penguins. Consumption of penguins increased, and of seal carrion declined, as chick-rearing progressed, mirroring the decreasing availability of the latter after the peak pupping period in December at South Georgia. Comparisons with data from 1979/80-1980/81 suggest some changes in giant petrel diets; however, these differences were no greater than the typical annual variation, and there were no clear links between diet and breeding allochrony or the differing population trends (more rapid increase in northern than southern giant petrels). The high diet diversity and ability of giant petrels to exploit both carrion and marine prey facilitates coexistence with other sympatric Procellariiformes and explains their favourable population status., Author(s): William F. Mills [sup.1] [sup.2] , Tim I. Morley [sup.1] , Stephen C. Votier [sup.3] , Richard A. Phillips [sup.1] Author Affiliations: (1) grid.478592.5, 0000 0004 0598 3800, British [...]

Prions Pachyptila are the most abundant seabirds in the Southern Ocean and comprise two main groups: those with and without bill lamellae to filter zooplankton. With few exceptions, each breeding location supports at most one species from each of these groups. However, Gough Island supports two morphologically very similar, filter-feeding species: broad-billed P. vittata and MacGillivray's prions P. macgillivrayi. To understand how these two species co-occur in sympatry, we compared the foraging ranges, habitat selectivity, trophic segregation and moult schedules of these species using combined geolocation-immersion loggers. After breeding, both species showed a well-defined westward migration prior to moulting. Moult lasted 11-19 weeks and was significantly longer in MacGillivray's than broad-billed prions. Moulting birds occurred in specific areas within the Argentine Basin, with little overlap between the two species. Habitat analysis revealed species-specific preferences, in particular sea surface temperature. Activity patterns also differed; MacGillivray's prions spent more time in flight, which indicates a more active foraging strategy, relying less on filter feeding. Stable isotope ratios ([delta].sup.15N) in flight feathers were greater in MacGillivray's prion, which is consistent with its less specialized bill morphology resulting in feeding at a higher trophic level. Inter-specific spatial segregation was observed for most of the tracking period, in large part because broad-billed prions breed roughly 3 months earlier than MacGillivray's prions. At Tristan da Cunha, 250 km farther north, where only broad-billed prions breed, they departed, moulted and returned significantly later (15-17 days) than conspecifics from Gough Island, providing evidence for character displacement in sympatry with MacGillivray's prion., Author(s): Christopher W. Jones [sup.1], Richard A. Phillips [sup.2], W. James Grecian [sup.3], Peter G. Ryan [sup.1] Author Affiliations: (1) grid.7836.a, 0000 0004 1937 1151, FitzPatrick Institute of African Ornithology, [...]

Diet analyses can reveal important changes in seabird foraging ecology and, by inference, resource availability and predator-prey dynamics within the wider marine ecosystem. Here, we analysed stomach contents of 1544 grey-headed albatross Thalassarche chrysostoma (GHA) and black-browed albatross T. melanophris (BBA) chicks from Bird Island, South Georgia. We describe dietary shifts (1996-2017), and link those to annual prey availability indices and breeding success. Annual variability in diet was high, and long-term trends in the main components were broadly similar in both albatrosses. Fish consumption (by mass) generally increased over time. Mackerel icefish Champsocephalus gunnari occurrence increased in GHA diets, but was unrelated to local densities derived from fisheries/research cruises. Cephalopod consumption declined until the early 2000s, then plateaued, and the occurrence of the ommastrephid squid Martialia hyadesi declined over time in both albatrosses. In BBAs, Antarctic krill Euphausia superba consumption decreased over time. Conversely, Antarctic krill consumption by GHAs increased until the early 2000s, decreased until the mid-2010s, and increased again in 2017. Antarctic krill consumption was unrelated to local densities based on acoustic surveys, and did not correlate with breeding success. Remotely sensed chlorophyll-a within core foraging areas showed a positive relationship with Antarctic krill in GHA diets, but a negative relationship with M. hyadesi occurrence in both albatross diets. Dietary shifts had consequences for GHA breeding success, which was negatively related to the importance of the cranchiid Galiteuthis glacialis and positively related to M. hyadesi importance. These results highlight the complex mechanisms linking prey availability, diet and breeding success in albatrosses., Author(s): William F. Mills [sup.1] [sup.2], José C. Xavier [sup.1] [sup.3], Stuart Bearhop [sup.2], Yves Cherel [sup.4], Stephen C. Votier [sup.2], Claire M. Waluda [sup.1], Richard A. Phillips [sup.1] Author [...]

Divergent foraging strategies may emerge within a population due to a combination of physiological and environmental factors; yet to persist, neither strategy should offer a consistent selective advantage over the alternative in the long term. Murphy's petrels Pterodroma ultima from Henderson Island (24°20'S, 128°20'W) in the South Pacific Ocean are highly vagile, and exhibit two distinct foraging trip types during incubation; similar proportions of birds undertake either looping trips around the South Pacific Gyre to waters off Peru (hereafter 'East') or trips south-west of the colony towards the Subtropical Front ('South') (mean maximum ranges of c. 3800 or 2000 km from the colony, respectively). However, the relative benefits of the distinct trip types remain unclear. Through tracking birds with GPS and salt-water immersion loggers in 2015, the fine-scale foraging behaviour was examined for East (trip durations: 14.1-19.8 days, maximum ranges 2387-4823 km) and South trips (12.9-25.8 days, 1565-1991 km). Data on behaviour classified from GPS tracks, the number of wet bouts per hour (a proxy for landing rates) and wind speeds, were used to distinguish two distinct foraging modes: birds on East trips spent more time in directed movement, whereas those on South trips spent a greater proportion of time in area-restricted search (ARS) behaviour. East trips were associated with higher overall mass gain, and wet bouts occurred in equal proportions during directed movement and ARS behaviour. This suggests that in unproductive marine environments, it may be more profitable to maximise area covered to increase the chances of encountering prey. Analysis of lower-resolution geolocator data (collected from 2011 to 2014) indicated that individuals were largely consistent in trip type between years. Since birds that conducted East trips were 19% lighter on departure from the colony and experienced more frequent tailwinds on foraging trips, we speculate that these birds may benefit from reduced movement costs, whilst also experiencing reduced competition for foraging opportunities., Author(s): Thomas A. Clay [sup.1] [sup.2] [sup.3] , Steffen Oppel [sup.4] , Jennifer L. Lavers [sup.4] [sup.5] , Richard A. Phillips [sup.1] , M. de L. Brooke [sup.2] Author Affiliations: [...]

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 [...]

Top predators are critical to ecosystem function, exerting a stabilising effect on the food web. Brown skuas are opportunistic predators and scavengers. although skuas are often the dominant land-based predator at seabird colonies, this is the first detailed study of their movements and activity during breeding. The study was carried out at Bird Island, South Georgia (54°00'S, 38°03'W), in the austral summer of 2011/2012 and included GPS data from 33 breeding adults tracked during the late incubation and early chick-rearing periods. Brown skuas spent on average more than 80 % of time in the territory, and it was extremely rare for both partners to leave the territory simultaneously. Much more time was spent foraging at the coast than in penguin colonies and, based on saltwater immersion data, adults never foraged at sea. None of the tracked birds appeared to specialise in catching small petrels at night. Fewer foraging trips were made per day, and hence, more time was spent in the territory, during incubation than chick-rearing. Despite the pronounced sexual size dimorphism, there were no effects of sex on territorial attendance, foraging time or habitat use. Skuas at Bird Island show higher territorial attendance and are less likely to leave the territory unattended than those breeding elsewhere, suggesting closer proximity to more diverse or abundant food resources than at other colonies. The results tie in with previous diet studies, indicating that brown skuas at this site feed mostly on seal placentae and carrion and that birds may rely on a broader range of food resources as the season progresses., Introduction Top predators can exert an important stabilising effect on the food web, keeping prey species in check and preventing the loss of inferior competitors (Paine 1966; Soule et al. [...]

Miniature geolocator loggers (Global Location Sensing, GLS) that provide daily locations of birds have revolutionised the study of winter ecology and migration patterns of seabirds. A long-term study of ringing recoveries and analyses of heavy metals and pollutants in tissues of Atlantic puffins Fratercula arctica from the Isle of May, south-east Scotland, suggested that this population wintered mainly within the North Sea. However, deployment of GLS devices over the 2007/2008 winter showed that many breeding birds made major excursions into the east Atlantic. This winter was the second of two when survival was extremely low (survival in 2006/2007 and 2007/2008 was 0.696 and 0.695, respectively, compared to the average of 0.922 over the period 1984/1985-2005/2006). These low rates of survival suggested that the unexpected use of the Atlantic might have been associated with unusually poor conditions in the North Sea as indicated by very low breeding success in 2007. Survival rate returned to previous levels in 2008/2009 providing the opportunity to test whether higher survival was associated with birds remaining in the North Sea, or whether movements into the Atlantic are a feature of this population unrelated to survival. Accordingly, geolocators were deployed over the 2009/2010 winter when adult survival was subsequently established to be high (0.913). We found greater support for the hypothesis that winter distribution is not associated with survival. Thus, 8 (40 %) of 20 individuals followed in 2009/2010 went into the Atlantic, a rate not significantly different from 11 (58 %) of the 19 followed in the 2007/2008 winter. Indeed, birds actually spent longer in the Atlantic and used a wider variety of areas in 2009/2010, although the time spent away from the colony was significantly shorter than in 2007/2008. Since our data were from individuals that survived, remaining in or moving out of the North Sea can both be successful strategies during winters when the population as a whole shows either high or low survival rates. Unfortunately, we do not know where birds that died had gone, and hence, the relative survival of birds that did or did not move into the Atlantic. Determining the link between survival and wintering area for any seabird remains a formidable challenge and will have to await the development of technologies that can determine both where and when birds die., Introduction Although the breeding biology of many seabirds is well documented, until recently there was a major gap in our knowledge of seabird migration and wintering areas. What little information [...]

Sexual segregation in foraging habitat occurs in many marine predators and is usually attributed to competitive exclusion, different parental roles of each sex or niche specialisation associated with sexual size dimorphism. However, relatively few studies have attempted to understand the patterns and underlying drivers of local-scale sexual segregation in marine predators. We studied habitat use, diet and feeding ecology of female and male wandering albatrosses Diomedea exulans, fitted with GPS and stomach-temperature loggers during the chick-rearing period (austral winter) at South Georgia in 2009. During this period, when oceanographic conditions were anomalous and prey availability was low in waters near the breeding colony, the tracked wandering albatrosses showed high consistency in their foraging areas at a large spatial scale, and both males and females targeted sub-Antarctic and subtropical waters. Despite consistency in large-scale habitat use, males and females showed different foraging behaviours in response to oceanographic conditions at a smaller scale. Males appeared to be more opportunistic, scavenging for offal or non-target fish discarded by fishing vessels in less productive, oceanic waters. They exhibited sinuous movements, feeding mostly on large prey and consuming similar amounts of food during the outbound and return parts of the foraging trip. In contrast, females targeted natural productivity hotspots, and fed on a wide variety of fish and cephalopods. They commuted directly to these areas; most prey were ingested on the outbound part of the trip, and they often started their return after ingesting large prey at the farthest point from the colony. Together, these results indicate that sexual segregation in core foraging areas of wandering albatrosses is driven by sex-specific habitat selection due to the low availability of prey in local Antarctic waters. This segregation results in different feeding behaviour at local scales which may be explained by differing breeding roles and degree of parental investment by each sex, with females investing more than males in reproduction. Further investigations are necessary to confirm the existence of this pattern through time under contrasting environmental conditions and to identify the drivers responsible for local-scale sexual segregation in wandering albatrosses., Author(s): Jorge M. Pereira [sup.1] , Vítor H. Paiva [sup.1] , Richard A. Phillips [sup.2] , José C. Xavier [sup.1] [sup.2] Author Affiliations: (Aff1) 0000 0000 9511 4342, grid.8051.c, MARE [...]

The distribution of Atlantic puffins (Fratercula arctica) from Skellig Michael, south-west Ireland, was investigated using geolocation loggers between the 2010 and 2011 breeding seasons. All tracked birds travelled rapidly west into the North Atlantic at the end of the breeding season in August, with the majority undertaking transatlantic trips from Ireland to the Newfoundland-Labrador shelf. The furthest distance from the colony reached by each bird was not influenced by body mass or sex and was achieved in approximately 20 days. By October, all birds had moved back to the mid Atlantic where they remained resident until returning to the breeding colony. The most parsimonious explanation for the rapid, directed long-distance migration is that birds exploit the seasonally high abundance of prey [e.g., fish species such as capelin (Mallotus villosus) and sandlance (Ammodytes spp.)] off the Canadian coast, which is also utilised by large populations of North American seabirds at this time. Once the availability of this short-term prey resource has diminished, the tracked puffins moved back towards the north-east Atlantic. A relationship between relative abundance of puffins and zooplankton was found in all winter months, but after correcting for spatial autocorrelation, was only significant in November and January. Nevertheless, these results suggest a potential switch in diet from mainly fish during the breeding and early post-breeding periods to zooplankton over the remaining winter period. This study suggests that puffins from south-west Ireland have a long-distance migration strategy that is rare in breeding puffins from the UK and identifies a key non-breeding destination for puffins from Ireland. This has implications for the susceptibility of different breeding populations to the effects of possible climatic or oceanographic change., Introduction Most seabirds undertake long migrations following the breeding season. This behaviour is thought to be an adaptive strategy to avoid seasonal deterioration in climate or increasing scarcity of resources [...]

The time seabirds have to forage is restricted while breeding, as time at sea must be balanced against the need to take turns with the partner protecting the nest site or offspring, and timing constraints change once the breeding season is over. Combined geolocator-immersion devices were deployed on eleven Imperial Shags (four males and seven females) in Argentina (43°04'S; 64°2'W) in November 2006 and recovered in November 2007. During the breeding season, females foraged throughout the morning, males exclusively in the afternoon, and variability between individuals was low. Outside the breeding season, both sexes foraged throughout the day, and variability between individuals was high. Timing differences may be explained by higher constraints on foraging or greater demands of parental duties experienced by the smaller sex, females in this case. Sexual differences in reproductive role, feeding habits or proficiency can also lead to segregation in timing of foraging, particularly while breeding., Introduction When breeding, seabirds are central-place foragers, forced to adjust their feeding behavior to satisfy the energetic demand of their offspring, as well as their own, under time constraints imposed [...]

There is an urgent need to identify key marine areas for conservation, particularly in the high seas. A range of techniques have been applied to tracking data from higher predators, particularly seabirds and pinnipeds, to determine the areas of greatest use. This study compared three commonly used methods--kernel, first-passage time and state-space modelling--and a new approach, minimum displacement rate, for the analysis of data from the wandering albatross Diomedea exulans of Bird Island, South Georgia, tracked during the chick-rearing period. Applied to a single track, these four models identified similar marine areas as important. The greatest similarity in areas identified occurred when model assumptions were shared (such as slow speed indicating spatial preference) even when methods modelled these assumptions differently (e.g. Bayesian inference versus cumulative density surface). A gridded overlap approach applied to all tracks revealed core areas not apparent from results of any single analysis. The gridded approach also revealed spatial overlap between methods based on different assumptions (e.g. minimum displacement rate and kernel analysis) and between individuals. Although areas identified as important by kernel and first-passage time analysis of a single track were biased towards resting locations during darkness, this does not negate the requirement for their protection. Using the gridded overlap approach, two distinct core regions were identified for the wandering albatross; one close to the breeding colony and another 800 km to the North-West in the high seas. This convenient and pragmatic approach could be applied to large data sets and across species for the identification of a network of candidate marine protected areas in coastal and pelagic waters., Introduction The last two decades have seen a marked increase in research using tracking technologies to understand the ecology and behaviour of animals (Phillips et al. 2007; Aarts et al. [...]

The wandering albatross (Diomedea exulans)is regarded as a generalist predator, but can it be consistent in its foraging niche at an individual level? This study tested short- and long-term consistency in the foraging niche in terms of habitat use, trophic level and, by inference, prey selection. Fieldwork was carried out at Bird Island, South Georgia, in May-October 2009, during the chick-rearing period. Blood (plasma and cells) and feathers for stable isotope analyses (δ[sup.13]C and δ[sup.15]N) were sampled from 35 adults on their return from a foraging trip during which they carried stomach temperature, activity and global positioning system loggers. Results suggest short-term consistency in foraging niche in relation to both oceanic water mass and trophic level, and long-term consistency in use of habitat. Consistent differences between individuals partly reflected sex-specific habitat preferences. The proportion of consistent individuals (i.e., with a narrow foraging niche) was estimated at c. 40 % for short-term habitat and trophic level (prey) preferences and 29 % for longer-term habitat preference, suggesting this is an important characteristic of this population and potentially of pelagic seabirds in general. Foraging consistency was not related to body condition or level of breeding experience; instead, it may reduce intraspecific competition., Introduction According to optimal foraging theory, animals should distribute themselves to maximize their foraging efficiency, which, during breeding, is dependent upon the ability to find food within the range of [...]

Considerable attention has focused on inter- and intraspecific variation in trophic niches of marine predators. Although this has revealed evidence for sexual segregation in distribution in some species, few studies have been able to address sex-related dietary specialisation. Stable isotope analysis of blood cells collected from albatrosses and petrels at South Georgia during chick-rearing indicated a difference in [delta].sup.13C, suggesting that females fed to the north of males, only in two species with male-biased sexual size dimorphism; in no species did sexes differ in trophic level ([delta].sup.15N). Based on a wider review, significant differences between sexes in isotope signatures were much more common in seabirds during the pre-laying or breeding than the nonbreeding period, presumably reflecting greater between-sex partitioning of resources when foraging ranges are more constrained and competition is greater. Sex differences, or their absence, were usually consistent across successive stages during the pre-laying and breeding periods, but not necessarily year-round nor between populations. Significant differences in isotope signatures between males and females were extremely rare in monomorphic species, suggesting a link between sexual size dimorphism and segregation in diet or distribution. Among the Southern Ocean albatrosses, sex differences in [delta].sup.13C suggested the underlying mechanism was related to habitat specialisation, whereas in other size-dimorphic taxa (both male- and female-biased), sex differences were more common in [delta].sup.15N than [delta].sup.13C and therefore more consistent with size-mediated competitive exclusion or dietary specialisation., Author(s): Richard A. Phillips [sup.1] , Rona A. R. McGill [sup.2] , Deborah A. Dawson [sup.3] , Stuart Bearhop [sup.4] Author Affiliations: (1) grid.8682.4, 0000000094781573, British Antarctic Survey, Natural Environment [...]

Despite the recent burgeoning in predator tracking studies, few report on seabird activity patterns, despite the potential to provide important insights into foraging ecology and distribution. In the first year-round study for any small petrel, we examined the activity patterns of the white-chinned petrel Procellaria aequinoctialis based on data from combination geolocator-immersion loggers deployed on adults at South Georgia. The petrels were highly nocturnal, flying for greater proportions of darkness than any large procellarid studied so far, except the light-mantled albatross Phoebetria palpebrata. Flight bout durations were short compared with other species, suggesting a dominant foraging mode of small-scale searching within large prey patches. When migrating, birds reduced the proportion of time on the water and increased flight bout duration. Activity patterns changed seasonally: birds flew least during the nonbreeding period, and most frequently during chick-rearing in order to meet higher energy demands associated with provisioning offspring. The degree of their response to moonlight was also stage dependent (greatest in nonbreeding, and weakest in incubating birds), a trait potentially shared by other nocturnal petrels which will have repercussions for feeding success and prey selection. For the white-chinned petrel, which is commonly caught in longline fisheries, these results can be used to identify periods when birds are most susceptible to bycatch, and therefore when use of mitigation and checking for compliance is critical., Author(s): Elizabeth K. Mackley [sup.1] [sup.2] , Richard A. Phillips [sup.1] , Janet R. D. Silk [sup.1] , Ewan D. Wakefield [sup.1] , Vsevolod Afanasyev [sup.1] , Robert W. Furness [...]

Most seabirds die outside the breeding season, but understanding the key factors involved is hampered by limited knowledge of nonbreeding distributions. We used miniature geolocating loggers to examine the movements between breeding seasons of Atlantic puffins Fratercula arctica from a major North Sea colony where numbers have declined in recent years, apparently due to increased overwinter mortality. The most intensively used region was the northwestern North Sea but most puffins also made excursions into the east Atlantic in the early winter. Ringing recoveries previously indicated that adults from British east coast colonies remained within the North Sea and hence were spatially segregated from those breeding on the west throughout the year. Updated analyses of ringing recoveries support results from geolocators suggesting that usage of Atlantic waters is a recent phenomenon. We propose that the increased adult mortality is related to changes in distribution during the nonbreeding period and reflects worsening conditions in the North Sea., Author(s): Michael P. Harris [sup.1] , Francis Daunt [sup.1] , Mark Newell [sup.1] , Richard A. Phillips [sup.2] , Sarah Wanless [sup.1] Author Affiliations: (1) grid.8682.4, 0000000094781573, Centre for Ecology [...]

Author(s): Michael P. Harris [sup.1] , Francis Daunt [sup.1] , Mark Newell [sup.1] , Richard A. Phillips [sup.2] , Sarah Wanless [sup.1] Author Affiliations: (1) grid.8682.4, 0000000094781573, Centre for Ecology [...]

Studies of avian migration increasingly use stable isotope analysis to provide vital trophic and spatial markers. However, when interpreting differences in stable isotope values of feathers, many studies are forced to make assumptions about the timing of moult. A fundamental question remains about the consistency of these values within and between feathers from the same individual. In this study, we examine variation in carbon and nitrogen isotopes by sub-sampling feathers collected from the wings of adults of two small congeneric petrel species, the broad-billed Pachyptila vittata and Antarctic prion P. desolata. Broad-billed prion feather vane material was enriched in N compared to feather rachis material, but there was no detectable difference in δC. Comparison of multiple samples taken from Antarctic prion feathers indicated subtle difference in isotopes; rachis material was enriched in C compared to vane material, and there were differences along the length of the feather, with samples from the middle and tip of the feather depleted in N compared to those from the base. While the greatest proportion of model variance was explained by differences between feathers and individuals, the magnitude of these within-feather differences was up to 0.5 ‰ in δN and 0.8 ‰ in δC. We discuss the potential drivers of these differences, linking isotopic variation to individual-level dietary differences, movement patterns and temporal dietary shifts. A novel result is that within-feather differences in δC may be attributed to differences in keratin structure within feathers, suggesting further work is required to understand the role of different amino acids. Our results highlight the importance of multiple sampling regimes that consider both within- and between-feather variation in studies using stable isotopes. [ABSTRACT FROM AUTHOR]

Studies of avian migration increasingly use stable isotope analysis to provide vital trophic and spatial markers. However, when interpreting differences in stable isotope values of feathers, many studies are forced to make assumptions about the timing of moult. A fundamental question remains about the consistency of these values within and between feathers from the same individual. In this study, we examine variation in carbon and nitrogen isotopes by sub-sampling feathers collected from the wings of adults of two small congeneric petrel species, the broad-billed Pachyptila vittata and Antarctic prion P. desolata . Broad-billed prion feather vane material was enriched in 15 N compared to feather rachis material, but there was no detectable difference in δ 13 C. Comparison of multiple samples taken from Antarctic prion feathers indicated subtle difference in isotopes; rachis material was enriched in 13 C compared to vane material, and there were differences along the length of the feather, with samples from the middle and tip of the feather depleted in 15 N compared to those from the base. While the greatest proportion of model variance was explained by differences between feathers and individuals, the magnitude of these within-feather differences was up to 0.5 ‰ in δ 15 N and 0.8 ‰ in δ 13 C. We discuss the potential drivers of these differences, linking isotopic variation to individual-level dietary differences, movement patterns and temporal dietary shifts. A novel result is that within-feather differences in δ 13 C may be attributed to differences in keratin structure within feathers, suggesting further work is required to understand the role of different amino acids. Our results highlight the importance of multiple sampling regimes that consider both within- and between-feather variation in studies using stable isotopes.