Predicting the foraging patterns of wintering Auks using a sea surface temperature model for the Barents Sea

1. The conservation of seabirds is increasingly important for their role as indicator species of ocean ecosystems, which are predicted to experience increasing levels of exploitation this century. Safeguarding these ecosystems will require predictive, spatial studies of seabird foraging hotspots. Current research on seabird foraging hotspots has established a significant relationship between probability of presence and several environmental variables, including Sea Surface Temperature (SST). However, inter-annual, basin-wide variation has the potential to invalidate these models, which depend on seasonal mesoscale variability. 2. In this study, we present a novel solution to predict presence from spatially and temporally variable environmental predictors, while reducing the influence of large-scale basin-wide variation. We model the Maximum Entropy (MaxENT) Model-derived relationship between Standardized Monthly SST (StdSST) and Habitat Suitability using Gaussian curve models, and then apply these models to independent StdSST data to produce heatmaps of predicted seabird presence. 3. In this study, we demonstrate StdSST to be a functional environmental predictor of seabird presence, within a Gaussian curve model framework. We demonstrate accurate predictions of the model’s training data and of independent seabird presence data to a high degree of accuracy (area under the receiver operator characteristic curve > 0.65) for four species of Auk: Common Guillemots (Uria aalge), Razorbills (Alca torda), Atlantic Puffins (Fratercula arctica) and Brunnich’s Guillemots (Uria lomvia). 4. We believe that the methodology we have developed and tested in this study can be used to guide ecosystem management practices by converting coupled-climate model predictions into predictions of future presence based on Habitat Suitability for the species, allowing us to consider the possible effects of climate change and yearly variation of SST on foraging seabird hotspots in the Barents Sea Atlantic Puffin, Barents Sea, Brunnich’s Guillemot, Common Guillemot, ecological modelling, MaxENT, Razorbill, spatial ecologypublishedVersio

Predicting the foraging patterns of wintering Auks using a sea surface temperature model for the Barents Sea

1. The conservation of seabirds is increasingly important for their role as indicator species of ocean ecosystems, which are predicted to experience increasing levels of exploitation this century. Safeguarding these ecosystems will require predictive, spatial studies of seabird foraging hotspots. Current research on seabird foraging hotspots has established a significant relationship between probability of presence and several environmental variables, including Sea Surface Temperature (SST). However, inter-annual, basin-wide variation has the potential to invalidate these models, which depend on seasonal mesoscale variability. 2. In this study, we present a novel solution to predict presence from spatially and temporally variable environmental predictors, while reducing the influence of large-scale basin-wide variation. We model the Maximum Entropy (MaxENT) Model-derived relationship between Standardized Monthly SST (StdSST) and Habitat Suitability using Gaussian curve models, and then apply these models to independent StdSST data to produce heatmaps of predicted seabird presence. 3. In this study, we demonstrate StdSST to be a functional environmental predictor of seabird presence, within a Gaussian curve model framework. We demonstrate accurate predictions of the model’s training data and of independent seabird presence data to a high degree of accuracy (area under the receiver operator characteristic curve > 0.65) for four species of Auk: Common Guillemots (Uria aalge), Razorbills (Alca torda), Atlantic Puffins (Fratercula arctica) and Brunnich’s Guillemots (Uria lomvia). 4. We believe that the methodology we have developed and tested in this study can be used to guide ecosystem management practices by converting coupled-climate model predictions into predictions of future presence based on Habitat Suitability for the species, allowing us to consider the possible effects of climate change and yearly variation of SST on foraging seabird hotspots in the Barents Sea Atlantic Puffin, Barents Sea, Brunnich’s Guillemot, Common Guillemot, ecological modelling, MaxENT, Razorbill, spatial ecologypublishedVersio

The relationship between daily behavior, hormones, and a color dimorphism in a seabird under natural continuous light

Author's accepted version (postprint).This is an Accepted Manuscript of an article published by Elsevier in Hormones and Behavior on 08/02/2021.Available online: https://www.sciencedirect.com/science/article/pii/S0018506X2100009X?via%3DihubThe predictable oscillation between the light of day and the dark of night across the diel cycle is a powerful selective force that has resulted in anticipatory mechanisms in nearly all taxa. At polar latitude, however, this oscillation becomes highly attenuated during the continuous light of polar day during summer. A general understanding of how animals keep time under these conditions is poorly understood. We tested the hypothesis that the common murre (a seabird, Uria aalge) can use melatonin and corticosterone, hormones associated with timekeeping, to track the diel cycle despite continuous light. We also tested the assumption that common murres breeding during polar summer schedule their colony attendance by time of day and sex, as they do at subpolar latitude. In the Atlantic population, common murres have a plumage color dimorphism associated with fitnessrelated traits, and we investigated the relationship of this dimorphism with colony attendance, melatonin, and corticosterone. The common murres did not schedule their attendance behavior by time of day or sex, yet they had higher concentrations of melatonin and, to a more limited extent, corticosterone during “night” than “day”. Melatonin also linked to behavioral state. The two color morphs tended to have different colony-attendance behavior and melatonin concentrations, lending support for balancing selection maintaining the plumage dimorphism. In common murres, melatonin can signal time of day despite continuous light, and the limited diel variation of corticosterone contributes to the mounting evidence that polar-adapted birds and mammals require little or no diel variation in circulating glucocorticoids during polar day. Arctic Circadian rhythm Color dimorphism Continuous light Corticosterone profile Daily rhythm Glucocorticoid profile Melatonin profile Midnight sun Uria aalgeacceptedVersio

Differences in Trophic Level, Contaminant Load, and DNA Damage in an Urban and a Remote Herring Gull (Larus argentatus) Breeding Colony in Coastal Norway

Herring gulls (Larus argentatus) are opportunistic feeders, resulting in contaminant exposure depending on area and habitat. We compared contaminant concentrations and dietary markers between two herring gull breeding colonies with different distances to extensive human activity and presumed contaminant exposure from the local marine diet. Furthermore, we investigated the integrity of DNA in white blood cells and sensitivity to oxidative stress. We analyzed blood from 15 herring gulls from each colony—the urban Oslofjord near the Norwegian capital Oslo in the temperate region and the remote Hornøya island in northern Norway, on the Barents Sea coast. Based on d13C and d34S, the dietary sources of urban gulls differed, with some individuals having a marine and others a more terrestrial dietary signal. All remote gulls had a marine dietary signal and higher relative trophic level than the urban marine feeding gulls. Concentrations (mean ± standard deviation [SD]) of most persistent organic pollutants, such as polychlorinated biphenyl ethers (PCBs) and perfluorooctane sulfonic acid (PFOS), were higher in urban marine (PCB153 17 ± 17 ng/g wet weight, PFOS 25 ± 21 ng/g wet wt) than urban terrestrial feeders (PCB153 3.7 ± 2.4 ng/g wet wt, PFOS 6.7 ± 10 ng/g wet wt). Despite feeding at a higher trophic level (d15N), the remote gulls (PCB153 17 ± 1221 ng/g wet wt, PFOS 19 ± 1421 ng/g wet wt) were similar to the urban marine feeders. Cyclic volatile methyl siloxanes were detected in only a few gulls, except for decamethylcyclopentasiloxane in the urban colony, which was found in 12 of 13 gulls. Only hexachlorobenzene was present in higher concentrations in the remote (2.6 ± 0.42 ng/g wet wt) compared with the urban colony (0.34 ± 0.33 ng/g wet wt). Baseline and induced DNA damage (doublestreak breaks) was higher in urban than in remote gulls for both terrestrial and marine feeders.publishedVersio

Twilight foraging enables European shags to survive the winter across their latitudinal range

Species breeding at high latitudes face a significant challenge of surviving the winter. Such conditions are particularly severe for diurnal marine endotherms such as seabirds. A critical question is therefore what behavioural strategies such species adopt to maximise survival probability. We tested 3 hypotheses: (1) they migrate to lower latitudes to exploit longer day length (‘sun-chasing’), (2) they forage at night (‘night-feeding’), or (3) they target high-quality food patches to minimise foraging time (‘feasting’). We studied the winter migration and foraging strategies of European shags Phalacrocorax aristotelis from 6 colonies across a latitudinal gradient from temperate regions to north of the Arctic Circle using geolocators deployed over 11 winters. We found evidence for ‘sun-chasing’, whereby average southerly movements were greatest from colonies at higher latitudes. However, a proportion of individuals from higher latitudes remained resident in winter and, in the absence of daylight, they foraged during twilight and only very occasionally during the night. At lower latitudes, there was little evidence that individuals migrated south, nocturnal feeding was absent, and twilight feeding was infrequent, suggesting that there was sufficient daylight in winter. There was no evidence that winter foraging time was lowest at higher latitudes, as predicted by the ‘feasting’ hypothesis. Our results suggest that shags adopt different behavioural strategies to survive the winter across their latitudinal range, dictated by the differing light constraints. Our study highlights the value of multi-colony studies in testing key hypotheses to explain population persistence in seabird species that occur over large latitudinal ranges

Six pelagic seabird species of the North Atlantic engage in a fly-and-forage strategy during their migratory movements

Bird migration is commonly defined as a seasonal movement between breeding and non-breeding grounds. It generally involves relatively straight and directed large-scale movements, with a latitudinal change, and specific daily activity patterns comprising less or no foraging and more traveling time. Our main objective was to describe how this general definition applies to seabirds. We investigated migration characteristics of 6 pelagic seabird species (little auk Alle alle, Atlantic puffin Fratercula arctica, common guillemot Uria aalge, Brünnich’s guillemot U. lomvia, black-legged kittiwake Rissa tridactyla and northern fulmars Fulmarus glacialis). We analysed an extensive geolocator positional and saltwater immersion dataset from 29 colonies in the North-East Atlantic and across several years (2008-2019). We used a novel method to identify active migration periods based on segmentation of time series of track characteristics (latitude, longitude, net-squared displacement). Additionally, we used the saltwater immersion data of geolocators to infer bird activity. We found that the 6 species had, on average, 3 to 4 migration periods and 2 to 3 distinct stationary areas during the non-breeding season. On average, seabirds spent the winter at lower latitudes than their breeding colonies and followed specific migration routes rather than non-directionally dispersing from their colonies. Differences in daily activity patterns were small between migratory and stationary periods, suggesting that all species continued to forage and rest while migrating, engaging in a ‘fly-and-forage’ migratory strategy. We thereby demonstrate the importance of habitats visited during seabird migrations as those that are not just flown over, but which may be important for re-fuelling.publishedVersio

Temperature synchronizes temporal variation in laying dates across European hole-nesting passerines

Publisher Copyright: © 2022 The Authors. Ecology published by Wiley Periodicals LLC on behalf of The Ecological Society of America.Identifying the environmental drivers of variation in fitness-related traits is a central objective in ecology and evolutionary biology. Temporal fluctuations of these environmental drivers are often synchronized at large spatial scales. Yet, whether synchronous environmental conditions can generate spatial synchrony in fitness-related trait values (i.e., correlated temporal trait fluctuations across populations) is poorly understood. Using data from long-term monitored populations of blue tits (Cyanistes caeruleus, n = 31), great tits (Parus major, n = 35), and pied flycatchers (Ficedula hypoleuca, n = 20) across Europe, we assessed the influence of two local climatic variables (mean temperature and mean precipitation in February–May) on spatial synchrony in three fitness-related traits: laying date, clutch size, and fledgling number. We found a high degree of spatial synchrony in laying date but a lower degree in clutch size and fledgling number for each species. Temperature strongly influenced spatial synchrony in laying date for resident blue tits and great tits but not for migratory pied flycatchers. This is a relevant finding in the context of environmental impacts on populations because spatial synchrony in fitness-related trait values among populations may influence fluctuations in vital rates or population abundances. If environmentally induced spatial synchrony in fitness-related traits increases the spatial synchrony in vital rates or population abundances, this will ultimately increase the risk of extinction for populations and species. Assessing how environmental conditions influence spatiotemporal variation in trait values improves our mechanistic understanding of environmental impacts on populations.Peer reviewe

Seabirds, climate and prey. A population study of two seabird species.

Many seabird populations have declined dramatically over recent decades, and studying the demography and population dynamic in seabird populations is important to gaining a better understanding of causes and mechanisms lying behind such changes and to identify targets for conservation and management. Climate and prey availability are known to affect demography and population dynamics of seabirds. Climate is now changing and a warming of the ocean may lead to changed availability of prey species and will affect seabirds through their demographic traits and ultimately their abundance and distribution. The main aim of this thesis was to study the impact of climate and prey abundance on seabird demography and population dynamics, using two seabird populations; the black-legged kittiwake Rissa tridactyla and the Common guillemot Uria aalge breeding on Hornøya in NE Norway whose populations are declining in Norway. The first question addressed in the thesis was how environmental conditions affect the demography and population variability of kittiwakes and guillemots. The non-breeding distribution of the kittiwakes has recently been documented using year-round light-based geolocators, and we investigated the relationship between environmental conditions in these non-breeding areas and the adult survival of kittiwakes breeding on Hornøya. We found for the kittiwakes that Thecosomata, a group of pteropods (also called sea butterflies), in the Grand Banks/Labrador Sea area in winter and the capelin Mallotus villosus stock in Barents Sea in the pre-breeding season together explained as much as 52 % of the yearly variation in adult survival rate. Further we found that the availability of 0-group cod Gadus morhua was a much more important factor affecting demography and determining the population dynamics of the common guillemot in the Barents Sea than previously considered. The second question was which demographic trait drives the population dynamics of the steeply declining kittiwake population on Hornøya. We showed, by using demographic matrix modeling and LTRE analyses, that both the variability in breeding success (and hence the recruitment to the population) and adult survival rate contributed to the steep decline in the kittiwake population on Hornøya. The strong reduction in breeding success (and hence a decline in recruitment to the population) had, however, the highest impact. The final question was whether populations can adapt to environmental changes through micro-evolutionary processes. This study found that adult survival of the two different genetic colour morphs (bridled and non-bridled morph) of the common guillemot responded differently to yearly variability in sea surface temperatures. Colour dimorphism may, in this case serve as a genetic marker in the guillemot population, and can potentially visualize the direction of selection and micro-evolutionary processes driven by climate. The studies in this thesis contribute to the understanding of the population dynamic of two declining seabird species which are both on the Norwegian Red List, and to the directions of future studies and conservation targets of both species

Effekter av forurensning på bestandsutviklingen til måser

Måser er toppredatorer i det marine miljø, og er svært utsatt for miljøgifter. Hos arter som sildemåse (Larus fuscus), svartbak (Larus marinus) og polarmåse (Larus hyperboreus) er det dokumentert høye nivåer av organokloriner (OC), som nedsetter immunforsvaret og gir økt forekomst av sykdom, noe som medfører både redusert hekkesuksess og overlevelse av voksne. Selv om det er dokumentert en rekke negative effekter av OC på individer hos måser er effekten på bestandsnivå ukjent. Målsetningen med denne undersøkelsen har vært å gi kvantitative prognoser for bestandsutviklingen i måsebestander med høye nivåer av forurensning. For å kvantifisere effekten av dagens forurensningsnivå hos måsebestander på bestandsutviklingen, har vi benyttet oss av strukturerte demografiske modeller som simulerer bestandsutviklingen i et variabelt og stokastisk miljø. Som input i modellene har vi brukt data på overlevelse av voksne, hekkesuksess (rekruttering av unger) og kjønnsratio (frekvensen av hanner og hunner i avkom som produseres) fra studier gjort langs norskekysten og fra Bjørnøya. I normalfordelte miljø, hvor bestanden uten forurensning er tilnærmet stabil, vil de nivåene av forurensning en kjenner til i dag gjennomsnittlig resultere i en bestandsreduksjon på 28 % etter 50 år. Effekter av forurensning på bestandsutviklingen vil imidlertid være sterkt avhengig av miljøvariasjon (hekkebetingelsene). Under dårlige hekkebetingelser vil bestanden, uten forurensning, reduseres med 39 %, mens høye nivåer av OC vil forsterke denne nedgangen slik at den blir på 51 %. Under gode hekkebetingelser vil bestanden, uten forurensning, vokse med 64 %. Høye nivåer av forurensning vil imidlertid sterkt redusere denne veksten, slik at bestanden kun vokser med 35 %, og dermed muligheten bestanden har for å utnytte gode år til vekst og nyrekruttering. Kvantitativt ser denne effekten ut til å være den viktigste for bestandsutviklingen. Beregninger viser at sannsynligheten for at bestanden skal halveres i løpet av 50 år under normale miljøbetingelser er 31 % med forurensning og 12 % uten. Under dårlige hekkebetingelser er denne sannsynligheten henholdsvis 79 % med forurensning og 55 % uten. En simulering av en reduksjon i forurensningsnivåene på 30 % over tid har liten effekt under normale miljøforhold. Det reduserer sannsynligheten for en halvering av bestanden fra 31 % til 28 % etter 50 år. Under dårlige miljøforhold er tilsvarende tall 79 % og 69 %. Datagrunnlaget for å gi sikre prognoser for måsebestander som har høye nivåer av OC er i dag ikke tilstrekkelig. Kunnskapen om nivåer av OC i enkeltbestander er imidlertid gode, men det er behov for flere studier som undersøker hvilke effekter ulike nivåer av OC har på viktig demografiske trekk som overlevelse og rekruttering av hann og hunn avkom. Det er derfor nødvendig å utvikle et overvåkningsprogram hvor en samtidig studerer forurensningsnivå, voksenoverlevelse og rekruttering i enkeltbestander over flere år. polarmåse, sildemåse, svartbak, organokloriner, bestandsutvikling, Norge, Bjørnøya, Glaucous gull, lesser black-backed gull, black-backed gull, organochlorines, population trends, Norway, Bear islan

Sjøfugl i Barentshavet - vurderinger av sårbare arter, bestander, områder ogperioder basert på nyeste kunnskap (revidert utgave)

Fauchald, P., Erikstad, K. E. & Reiersten, T. K. 2019. Sjøfugl i Barentshavet - vurderinger av sårbare arter, bestander, områder og perioder basert på nyeste kunnskap (revidert utgave). NINA Rapport 1616b. Norsk institutt for naturforskning. Barentshavet har store bestander av sjøfugl som potensielt er sårbare for uhellsutslipp av olje fra eksisterende og planlagt petroleumsvirksomhet. I denne rapporten oppsummerer vi kunnskapsstatusen for sjøfuglbestandene i Barentshavet med hensyn til sårbarhet for oljeforurensning. Gjennom sjøfuglprogrammene SEAPOP og SEATRACK har det de siste årene vært samlet inn mye ny kunnskap om sjøfuglene i norske havområder. Ny loggerteknologi har gjort oss i stand til å følge de enkelte bestandene gjennom året, og vi oppsummerer kunnskapsstatus om hvordan de mest sårbare artene migrerer ut og inn av Barentshavet og hvor de til enhver tid oppholder seg. Hekkeperioden, svømmetrekk, og fjærfelling er perioder hvor spesielt alkefuglene er sårbare. Vi går gjennom ny kunnskap, muliggjort av detaljerte loggerstudier utført i disse periodene. Overvåking av demografi og populasjonsutvikling som gjennomføres i regi av SEAPOP, gjør at vi har god oversikt over bestandsstatusen til de viktigste og mest sårbare artene i Barentshavet. Basert på disse dataene kan vi ved hjelp av bestandsmodellering bestemme den enkelte hekkebestands sårbarhet for en akutt økning i dødelighet som følge av for eksempel et oljeuhell. I hekkeperioden (april-august) er sjøfuglene spesielt sårbare i områdene i umiddelbar nærhet til koloniene. SEAPOP har god oversikt over sjøfuglkoloniene på Svalbard og fastlands Norge, og studier med GPS-loggere gir oss detaljerte data over fuglenes aksjonsradius ut fra koloniene. Rett etter hekking gjennomfører lomvi, polarlomvi og alke et svømmetrekk til havområdene hvor fjærfelling foregår. Fuglene regnes for å være spesielt sårbare i denne perioden fordi de ikke kan fly, og dermed ikke så lett kan unnslippe forurensede områder. Tidlig på høsten er Barentshavet spesielt produktivt, og sjøfugl fra kolonier i Norskehavet migrerer i denne perioden inn i området for å beite. Flere bestander, og spesielt bestander som hekker i den vestlige delen, forlater Barentshavet sent på høsten. Hoveddelen av den norske bestanden av lomvi blir imidlertid igjen i et forholdsvis begrenset område sør i Barentshavet. Polarlomvi fra de store koloniene i nord og øst blir også igjen i Barentshavet gjennom vinteren. Det samme gjør de østlige bestandene av lunde. Sjøfuglbestandene vender tilbake mot hekkekoloniene allerede sent på vinteren. Gytevandringen til lodde mot kysten av Kola og Finnmark, er en viktig næringskilde for alkefugl og krykkje i denne perioden. Lomvibestanden i Barentshavet er voksende, men sett i et historisk perspektiv har den nylig kommet tilbake til samme nivå som den hadde etter den store bestands-nedgangen midt på 1980-tallet. Bestandene av polarlomvi, lunde og krykkje er imidlertid synkende, og økt dødelighet vil kunne øke risikoen for at disse bestandene når et kritisk lavt nivå. Miljørisikoanalyser av sjøfugl gjennomføres i dag ved bruk av datasett opparbeidet gjennom tak-sering av sjøfugl til havs. Fordi disse dataene representerer relative forekomster og ikke inneholder informasjon om bestandstilhørighet, har analysene først og fremst kunnet gi informasjon om sårbarhet relativt til område og sesong. Analysene har med andre ord i liten grad kunnet gi informasjon om sjøfuglenes sårbarhet på bestandsnivå. De nye datasettene som blir opparbeidet av SEATRACK gjør det for første gang mulig å koble forekomsten av sjøfugl til havs til hekkebe-standene. Dermed kan man nå i prinsippet fullt ut utnytte SEAPOP sine overvåkingsdata i miljø-risikosammenheng og spesifikt adressere risikoen for de enkelte sjøfuglbestandene ved et akutt oljesøl. I tillegg er man i ferd med å opparbeidet detaljert kunnskap om sjøfuglenes atferd til havs, og man er nå i stand til å generere realistiske modeller for sjøfuglenes bevegelse og utbredelsesmønster i særlig sårbare perioder og områder.Fauchald, P., Erikstad, K. E. & Reiersten, T. K. 2019. Seabird in the Barents Sea – an evaluation of vulnerable species, populations, areas and seasons based on new and updated data and knowledge (revised edition). NINA Report 1616b. Norwegian Institute for Nature Research. The Barents Sea holds large populations of seabirds that are potentially vulnerable to accidental oil spills from existing and planned petroleum activities. In this report, we summarize the knowledge status of the vulnerability of the Barents Sea seabird populations to oil pollution. In recent years, new knowledge has been gathered on this topic through the seabird monitoring programs SEAPOP and SEATRACK. In particular, new technology for bird tracking has enabled us to follow the movement of breeding populations throughout the year, and we summarize the present knowledge of the year-round spatial distribution of vulnerable populations, and when they eventually migrate in and out of the Barents Sea. The auk species are especially vulnerable during the breeding season, during the swim migration and during moulting. We summarize new knowledge, made possible by detailed tracking studies conducted during these periods. The monitoring of demography and population dynamics carried out by SEAPOP gives a comprehensive picture of the status of the most important and vulnerable seabird populations in the Barents Sea. Based on these data, we can, by means of population viability analyses (PVA), determine the individual breeding population's vulnerability to an acute in-crease in mortality due to, for example, an oil accident During the breeding season (April-August), the areas close to the large seabird colonies are especially vulnerable for acute oil spills. SEAPOP has mapped the seabird colonies in Svalbard and mainland Norway, and studies with GPS loggers have provided detailed data on the birds' radius of action from several colonies. Immediately after breeding, common guillemots, Brünnich’s guillemots and razorbills conduct a swim migration to the sea areas where they moult. The birds are vulnerable during this period because they cannot fly and thus cannot easily escape oil polluted areas. In the early autumn, the Barents Sea offers rich feeding conditions, and seabirds from colonies in the Norwegian Sea migrate into the Barents Sea for feeding. Some populations, especially those nesting in the western part, leave the Barents Sea in late fall. However, the major proportion of the Norwegian population of common guillemots over winter in a relatively limited area in the southern Barents Sea. Brünnich’s guillemots from the large colonies in the north and east remains also in the Barents Sea throughout the winter. The same goes for the eastern populations of puffins. The seabird populations return to the nesting colonies in late winter. The spawning migration of capelin from the central Barents Sea to the coast of Kola and Finnmark, is an important target for feeding auks and kittiwakes during late winter and spring. The population of common guillemots in the Barents Sea is growing, but seen from a historical perspective, it has recently returned to the same level as it had after the large population decline in the mid-1980s. The populations of the Brünnich’s guillemots, Atlantic puffin and black-legged kittiwakes are declining, and increased mortality may increase the risk of these populations reaching critically low levels. Environmental risk assessments of seabirds at sea are currently being carried out using data accumulated through seabirds at sea surveys. Because these data represent relative occurrences and do not identify the populations of the birds present, the analyzes have primarily been able to provide information of the relative vulnerability among areas and seasons and give limited information on the seabirds' vulnerability at the population level. The new datasets that are being developed by SEATRACK make it possible for the first time to link the occurrences of seabirds at sea to their breeding populations. Thus, one can now in principle fully utilize SEAPOP's monitoring data in environmental risk assessments and specifically address the risk of an acute oil spill for individual seabird populations. In addition, detailed knowledge of seabirds’ behavior at sea is developing, and it is now possible to generate realistic models for seabirds' movement and distribution patterns in particularly vulnerable periods and areas