Diel rhythms synchronized to Earth's photic cycle are near-ubiquitous among animals living in regions with distinct day-night cues. Where such cues are reduced or absent, however, activity patterns may weaken, reorganize or become decoupled from the light-dark cycle, which may allow for more flexible behavioural expression. Using a dataset of >900 free-ranging black-legged kittiwakes from colonies spanning a broad latitudinal gradient (40-81°N), we show considerable population-level variation in diel activity patterns, from clear 24 h rhythms with distinct peaks at dawn and dusk at lower latitudes, to variable and non-diel rhythms with flattened activity patterns across the 24 h day at high latitudes. These patterns were consistent with the wide spectrum of light-dark cycles experienced across their breeding range, supported by our finding that activity was strongly predicted by sun elevation, suggesting alignment with the light-dark cycle. Together, our findings reveal substantial within-species variation in rhythmicity across latitudes and demonstrate that changes in the photic environment can reshape the temporal organization of activity even within a single, widely distributed species.

Trace elements occur naturally in the environment, but anthropogenic activities can amplify their release, increasing exposure and bioaccumulation in marine predators such as seabirds. Mercury (Hg) in liver, blood, and eggs of Leach's storm-petrels (Hydrobates leucorhous), has been investigated as a short-term exposure indicator of hatching and fledging success. However, chronic Hg intake and exposure to other trace elements during the non-breeding period remain poorly understood. This study assessed geographic variation in trace element exposure and relative trophic position in Leach's storm-petrels from five overwintering locations in the Atlantic Ocean, using secondary feathers (S4s) and geolocation data. Hg concentrations and trophic position (δ15N) varied significantly among overwintering locations, whereas other trace elements varied without clear spatial patterns. Sea surface temperature was positively correlated with Hg concentrations, whereas dietary origin (δ13C) and year were associated with relative trophic position. Colony of origin had no effect on Hg or trophic position, likely reflecting high intra-colony variability in wintering locations. Additionally, Hg concentrations were highest in birds overwintering in oligotrophic regions where δ15N values were low, suggesting lower nitrogen baselines in areas dominated by diazotrophic organisms and enhanced methylmercury availability via sulfate-reducing bacteria. In contrast, storm-petrels overwintering in productive upwelling regions such as the Benguela system exhibited lower Hg concentrations, consistent with Hg biodilution driven by rapid decaying phytoplankton export to deep sediments. These findings provide baseline information on trace element exposure during the non-breeding period of Leach's storm-petrels and inform future studies on migratory carry-over effects influencing adult survival and reproductive success.

Highly pathogenic avian influenza clade 2.3.4.4b H5Nx viruses (HPAIVs) have caused significant mortality in wild birds. We investigated active avian influenza virus (AIV) infections and assessed seroprevalence based on general nucleoprotein-specific and H5-specific antibodies in seabirds in Atlantic Canada during 2022-2023. Results were compared to seroprevalence data from 2011 to 2016 to evaluate changes in infection rates following the incursion of HPAIV. We sampled 1073 wild live birds belonging to 14 species. Active H5Nx infections were detected only in 2022, with the highest prevalence in Common Murres (64%), followed by Black-legged Kittiwakes (13%). Differences in seroprevalence were observed between years and species, with both Common Murres and Atlantic Puffins exhibiting higher rates after HPAIV incursion, particularly for anti-H5-specific antibodies. Seroprevalence also differed between locations, and age-related differences in exposure were observed with juvenile birds having much lower seroprevalence than adult birds, particularly among gulls. Despite no active infections being detected in 2023, high seroprevalence across species suggests persisting immunity and/or recent virus circulation. These findings underscore the importance of serological monitoring in tracking AIV dynamics, as antibody detection provides critical insights into past HPAIV exposure even when active infection rates are low.

Pelagic seabirds are one of the most threatened bird groups globally. Attraction to, and disorientation by, artificial light at night (ALAN) is a key factor reducing survival of nocturnal, burrow nesting seabird species. To investigate whether Leach's storm-petrel (Hydrobates leucorhous) nestlings and juveniles stranded due to ALAN could be differentiated using biogeochemical markers, we compared ten trace element concentrations (As, Cd, Co, Cu, Hg, Mn, Pb, Tl, V, Zn) and two stable isotope values (δ13C and δ15N) in juvenile feathers. We expected stranded juveniles to have different trace element concentrations from those sampled in the nest, and dietary indicators in the same feathers (δ13C and δ15N) to differ between groups. We found that offshore stranded juveniles had higher trace element concentrations than inshore stranded juveniles and nestlings while concentrations for nestlings and inshore stranded juveniles were more similar. Both stable isotope values were higher in nestlings than in stranded juveniles, with δ13C being similar between inshore and offshore stranded birds, while δ15N was lower in offshore compared to inshore stranded juveniles. Our study shows that inshore and offshore stranded juveniles have distinctly different biogeochemical markers, raising questions about differences in the mechanisms underlying the likelihood of stranding at inshore and offshore locations.

Regional seabird population monitoring is often characterized by sparse and imprecise counts from a large number of colonies, which can vary in abundance by several orders of magnitude and may show complex and concordant trajectories over time. Analysis frameworks that account for these complexities are critically needed for accurate population status assessments. Here, we developed a Bayesian hierarchical model that shares trajectory information among colonies, accounts for observation error and missing data, and estimates population trends both at the level of individual colonies and at the larger regional scale. Simulations confirmed that the model produces unbiased trend estimates even with extremely sparse and imprecise counts, and with highly non-linear population trajectories. Application of the model to empirical data for Leach’s Storm-Petrel ( Hydrobates leucorhous ) showed that the regional population has strongly declined over three generations in eastern Canada and that most colonies experienced similar trajectories over that period, implying they are influenced by shared large-scale environmental drivers. Conversely, the regional Atlantic Puffin ( Fratercula arctica ) population has likely increased in eastern Canada over three generations but individual colonies experienced highly divergent trajectories, indicating that smaller-scale colony-level processes may play a stronger role for that species. This approach provides a powerful tool for more accurate assessments of seabird population status to inform their conservation.

Serological surveillance enhances our understanding of influenza A virus (IAV) exposure and dynamics in wild bird populations. Traditional serum-based testing, while effective, poses logistical challenges for large-scale surveillance, particularly in remote regions, for small-bodied species or in scenarios such as hunter-harvested samples where serum collection can be impractical. This study evaluates the use of whole blood collected on high-quality cellulose filter strips as an alternative to serum for detecting antibodies against IAV nucleoprotein (NP) and hemagglutinin (HA) H5 and H7 targets. We tested paired serum and whole blood on filter strips collected from wild birds using the commercially available IDEXX AI MultiS Screen Ab test and in-house competitive enzyme-linked immunosorbent assays (ELISAs) developed at the National Centre for Foreign Animal Disease (NCFAD) of the Canadian Food Inspection Agency. Strong correlations (ρ = 0.77) were observed between serum and whole blood on filter strips for NP detection with the IDEXX ELISA, while moderate correlations were noted for NCFAD's NP (ρ = 0.58) and H5 (ρ = 0.65) assays. Correlation between serum and whole blood on filter strips for NCFAD's H7 assay was poor, although interpretation is limited due to the small sample size of H7 positives. Threshold optimization using the Youden index improved diagnostic performance, with optimized cutoffs identified for NP (sample-to-negative < 0.7708 for IDEXX and percentage inhibition [PI] > 39.56 for NCFAD) and H5 (PI > 20.37). Storage conditions impacted performance, with frozen whole blood on filter strips achieving higher sensitivity compared to those stored at room temperature. These findings support the use of filter strips to collect whole blood as an informative alternative for IAV serological surveillance in wild birds when serum is unavailable, provided optimal storage conditions and threshold adjustments are implemented, although serum remains the superior sample type.

Ecosystem structure and biophysical processes mediate biological responses to climate changes, but few studies have examined impacts of this dynamic among upper trophic levels. We investigated ecosystem differences in how diverse seabird populations across the northern hemisphere have responded to changes in regional mixed layer temperature and water column stratification. Using 138 time series of breeding productivity over the past half-century, we show that seabird reproductive productivity has declined in the Arctic and North Atlantic but not in the Pacific during a period of ubiquitous mixed layer warming and regionally-variable stratification trends. Models of breeding productivity and ocean drivers show that seabird responses to climate change vary by ecosystem. Additionally, ecosystems in which seabirds exhibit detectibly declining productivity tend to have lower overall diet diversity across seabird species. These findings emphasize the importance of ecosystem processes and structure in determining the vulnerability of marine predators to climate change.

Aim: To identify the broad-scale oceanic migration routes ('marine flyways') used by multiple pelagic, long-distance migratory seabirds based on a global compilation of tracking data. Location: Global. Time Period: 1989-2023. Major Taxa Studied: Seabirds (Families: Phaethontidae, Hydrobatidae, Diomedeidae, Procellariidae, Laridae and Stercorariidae). Methods: We collated a comprehensive global tracking dataset that included the migratory routes of 48 pelagic and long-distance migrating seabird species across the Atlantic, Indian, Pacific and Southern Oceans. We grouped individuals that followed similar routes, independent of species or timings of migration, using a dynamic time warping clustering approach. We visualised the routes of each cluster using a line density analysis and used knowledge of seabird spatial ecology to combine the clusters to identify the broad-scale flyways followed by most pelagic migratory seabirds tracked to-date at an ocean-basin scale. Results: Six marine flyways were identified across the world's oceans: the Atlantic Ocean Flyway, North Indian Ocean Flyway, East Indian Ocean Flyway, West Pacific Ocean Flyway, Pacific Ocean Flyway and Southern Ocean Flyway. Generally, the flyways were used bidirectionally, and individuals either followed sections of a flyway, a complete flyway, or their movements linked two or more flyways. Transhemispheric figure-of-eight routes in the Atlantic and Pacific oceans, and a circumnavigation flyway in the Southern Ocean correspond with major wind-driven ocean currents. Main Conclusions: The marine flyways identified demonstrate that pelagic seabirds have similar and repeatable migration routes across ocean-basin scales. Our study highlights the need to account for connectivity in seabird conservation and provides a framework for international cooperation.

In a warming Arctic, circumpolar long-term monitoring programs are key to advancing ecological knowledge and informing environmental policies. Calls for better involvement of Arctic peoples in all stages of the monitoring process are widespread, although such transformation of Arctic science is still in its infancy. Seabirds stand out as ecological sentinels of environmental changes, and priority has been given to implement the Circumpolar SeabirdMonitoring Plan (CSMP). We assessed the representativeness of a pan-Arctic seabird monitoring network focused on the black-legged kittiwake (Rissa tridactyla) by comparing the distribution of environmental variables for all known versus monitored colonies. We found that with respect to its spatiotemporal coverage, this monitoring network does not fully embrace current and future environmental gradients. To improve the current scheme, we designed a method to identify colonies whose inclusion in the monitoring network will improve its ecological representativeness, limit logistical constraints, and improve involvement of Arctic peoples. We thereby highlight that inclusion of study sites in the Bering Sea, Siberia, western Russia, northern Norway, and southeastern Greenland could improve the current monitoring network and that their proximity to local populations might allow increased involvement of local communities. Our framework can be applied to improve existing monitoring networks in other ecoregions and sociological contexts.

Migratory species with disjunct and localized breeding distributions, including many colonial marine birds, pose challenges for management and conservation as their dynamics are shaped by both broad oceanographic changes and specific factors affecting individual breeding colonies. We compare six colonies of the declining Leach's storm-petrel, Hydrobates leucorhous, across their core range in Atlantic Canada using standard capture-mark -recapture methods to estimate annual survival of individually marked populations of breeding adults. Over the period analysed (5-20 years per colony; 2003-2022), mean annual survival varied among colonies (0.81-0.88) and annually (process error sigma ranging from 0.01 to 0.09), though annual fluctuations were not synchronous across colonies. Two colonies with limited natural predation showed higher survival, and there was a decline in survival with increasing colony-specific total mercury burden. Our work shows that colony-specific pressures and regional contaminant burdens are potentially important contributors to current population de-clines, and highlights the importance of monitoring demographic rates at multiple sites for species that congregate at key life-history stages.

Plastic pollution is distributed patchily around the world's oceans. Likewise, marine organisms that are vulnerable to plastic ingestion or entanglement have uneven distributions. Understanding where wildlife encounters plastic is crucial for targeting research and mitigation. Oceanic seabirds, particularly petrels, frequently ingest plastic, are highly threatened, and cover vast distances during foraging and migration. However, the spatial overlap between petrels and plastics is poorly understood. Here we combine marine plastic density estimates with individual movement data for 7137 birds of 77 petrel species to estimate relative exposure risk. We identify high exposure risk areas in the Mediterranean and Black seas, and the northeast Pacific, northwest Pacific, South Atlantic and southwest Indian oceans. Plastic exposure risk varies greatly among species and populations, and between breeding and non-breeding seasons. Exposure risk is disproportionately high for Threatened species. Outside the Mediterranean and Black seas, exposure risk is highest in the high seas and Exclusive Economic Zones (EEZs) of the USA, Japan, and the UK. Birds generally had higher plastic exposure risk outside the EEZ of the country where they breed. We identify conservation and research priorities, and highlight that international collaboration is key to addressing the impacts of marine plastic on wide-ranging species.

Seabirds are declining globally, though the threats they face differ among and within species and populations. Following substantial population declines at several breeding colonies, Leach's Storm-Petrel (Hydrobates leucorhous) was uplisted from Least Concern to Vulnerable by the International Union for Conservation of Nature (IUCN) in 2016. Reasons for these declines are unclear, and it is important to identify threats the species faces across its global breeding range to guide research directions and inform conservation efforts. We solicited feedback from 37 Leach's Storm-Petrel scientific experts from eight countries on the importance of different threats facing the species on land and at sea. Perceived threats to extant colonies varied spatially, with a consensus within regions for main threats. Most researchers agreed that the main threats at or near colonies are avian and mammalian predators and onshore light attraction. At-sea threats have been less studied and were harder to identify and rank, but include offshore lights and structures, spatial shifts in prey, and contaminants. Climate change was not listed specifically because of its multifaceted repercussions, but several perceived threats are linked to climate change. Globally, introduction of mammalian predators is an overarching driver of seabird colony decline or extirpation; thus biosecurity must be considered an important measure for the conservation of storm-petrels. In addition, filling knowledge gaps and implementing a series of regionally relevant and targeted strategies that lead to small but cumulative conservation successes may be the best approach for this species.

Many seabirds are attracted to anthropogenic light, and the risk is greater for recent fledglings. Lunar phase predicts the probability of stranding, but it remains uncertain whether lunar phase is associated with when young seabirds fledge. Fledging behaviour of nocturnal, burrowing seabirds can be difficult to monitor using traditional methods but can provide insight into environmental factors that influence the risk of stranding. We used passive integrated transponder tags to monitor the fledging dates and times of Leach’s Storm-Petrel chicks from four breeding seasons at a major colony in Newfoundland and Labrador, Canada. We also assessed whether lunar phase associated with fledging date. The median fledge time was 2.4 h after sunset (1.4 - 12.4 h). The median fledge date was 10 October, and fledging dates ranged from 13 September to 13 November. Most importantly, Leach’s Storm-Petrels chicks did fledge during the full moon. These results provide insight into why storm-petrels are less attracted to anthropogenic light during high levels of natural illumination and can be used to inform periods of higher risk for stranding, thus allowing better concentration of conservation efforts.

Mercury (Hg) is a globally distributed heavy metal, with negative effects on wildlife. Its most toxic form, methylmercury (MeHg), predominates in aquatic systems. Levels of MeHg in marine predators can vary widely among individuals and populations. Leach's storm-petrels (Hydrobates leucorhous) have elevated levels of Hg but the role of Hg in storm-petrel population declines is unknown. In this study, we used egg and blood samples to study variation in Hg exposure among several northwest Atlantic colonies during breeding seasons, thereby evaluating relative toxicity risk within and among colonies. Total mercury (THg) concentrations were higher with increasing colony latitude, and were more pronounced in blood than in eggs. THg concentrations in blood were mostly associated with low toxicity risk in birds from the southern colonies and moderate risks in birds from the northern colonies; however, those values did not affect hatching or fledging success. THg concentrations in both eggs and blood were positively correlated with δ34S, emphasizing the role of sulfate-reducing bacteria in methylation of THg acquired through marine food webs, which is consistent with enriched δ34S profiles. By associating tracking data from foraging trips with THg from blood, we determined that blood THg levels were higher when storm-petrel's intensive search locations were over deeper waters. We conclude that spatial variation in THg concentrations in Leach's storm-petrels is attributable to differences in ocean depth at foraging locations, both at individual and colony levels. Differences in diet among colonies observed previously are the most likely cause for observed blood THg differences. As one of the few pelagic seabird species breeding in Atlantic Canada, with limited overlap in core foraging areas among colonies, Leach's storm-petrels can be used as biomonitors for less sampled offshore pelagic regions. The global trend in Hg emissions combined with legacy levels warrant continued monitoring for toxicity effects in seabirds.

Abstract In the Arctic, chemical contaminants, shipping, oil pollution, plastic pollution, changing habitats in relation to climate change and fisheries have been identified as environmental stressors to seabirds such as Fulmarus glacialis (northern fulmar; qaqulluk; ᖃᖁᓪᓗᖅ), but rarely have these stressors been considered within a cumulative effects framework in this species which is currently showing a declining populations trend. As a novel tool to understand cumulative effects within a conservation context, we applied a fuzzy cognitive mapping (FCM) approach that allows experts to arrange key factors and their interrelationships, organizing their understanding of the components of a complex issue into a graphical representation; a ‘cognitive map’. This process was grounded in local environment concerns as documented in several Nunavut‐specific reports and discussions, and worked with western‐trained seabird experts with knowledge of northern fulmar populations to assess the inter‐related environmental threats to fulmars as a way to combine these stressors in a cumulative effects framework and identify conservation actions and knowledge gaps. We found strong agreement that the main stressors affecting northern fulmar populations in Canada include pollution (11% total influence (TI)), shipping activities (16% TI), hunting and fishing (18% TI) and mining/oil and gas exploitation activities (22% TI). The indirect influence of threats on northern fulmar population size (57% TI) exceeded the total direct influence (43% TI), emphasizing the value of cognitive mapping in cumulative effects assessment for a more holistic understanding of interacting stressors. Participants expressed substantial uncertainty regarding the strong relationships leading from the concepts, commercial fishing activity in the BBDS and the North Atlantic fisheries activity, indicating that these potential stressors require more research. Similarly, uncertainty was expressed about the potential effects of zodiac traffic, ship strikes of northern fulmar, number of oil spills and magnitude of oil spills on northern fulmar. By characterizing individual factors as manageable or not, we determined that stressors are largely manageable with enforcement of existing policies (58% TI)—importantly, fishing activities were both highly influential on fulmars and deemed manageable, which will inform ongoing co‐management planning in the region.

Many seabirds are attracted to anthropogenic light, and the risk is greater for recent fledglings. Moon phase predicts the probability of stranding (fewer birds strand on the full moon), but it remains uncertain whether moon phase is associated with when young seabirds fledge. Fledging behaviour of nocturnal, burrowing seabirds can be difficult to monitor using traditional methods but can provide insight into environmental factors that influence the risk of stranding. We used passive integrated transponder tags to monitor the fledging dates and times of Leach's storm-petrel (Hydrobates leucorhous) chicks across four breeding seasons (2017, 2018, 2021, 2022) at a major colony in Newfoundland and Labrador, Canada. We also assessed whether moon phase and incident illumination related to fledging date and time. The median fledge time was 1.6 h after sunset (0.6-11.7 h). The median fledge date was 10 October, and fledging dates ranged from 13 September to 13 November. Most importantly, moon phase was not associated with the time and date that Leach's storm-petrel chicks fledged. These results suggest that recently fledged storm-petrels are less attracted to anthropogenic light during high levels of natural illumination, which could indicate periods of higher stranding risk and help concentrate conservation efforts.

Conservation of mobile organisms is difficult in the absence of detailed information about movement and habitat use. While the miniaturization of tracking devices has eased the collection of such information, it remains logistically and financially difficult to track a wide range of species across a large geographic scale. Predictive distribution models can be used to fill this gap by integrating both telemetry and census data to construct distribution maps and inform conservation goals and planning. We used tracking data from 520 individuals of 14 seabird species in Atlantic Canada to first compare foraging range and distance to shorelines among species across colonies, and then developed tree-based machine-learning models to predict foraging distributions for more than 5000 breeding sites distributed along more than 5000 km of shoreline. Despite large variability in foraging ranges among species, tracking data revealed clusters of species using similar foraging habitats (e.g., nearshore vs. offshore foragers), and within species, foraging range was highly colony-specific. Even with this variability, distance from the nesting colony was an important predictor of distribution for nearly all species, while distance from coastlines and bathymetry (slope and ruggedness) were additional important predictors for some species. Overall, we demonstrated the utility of tree-based machine-learning approach when modeling tracking data to predict distributions at un-sampled colonies. Although tracking and colony data have some shortcomings (e.g., fewer data for some species), where results need to be interpreted with care in some cases, applying methods for modeling breeding season distributions of seabirds allows for broader-scale conservation assessment. The modeled distributions can be used in decisions about planning for offshore recreation and commercial activities and to inform conservation planning at regional scales.

Reproduction in procellariiform birds is characterized by a single egg clutch, slow development, a long breeding season and obligate biparental care. Female Leach's Storm Petrels Hydrobates leucorhous, nearly monomorphic members of this order, produce eggs that are between 20 and 25% of adult body weight. We tested whether female foraging behaviour differs from male foraging behaviour during the ~ 44-day incubation period across seven breeding colonies in the Northwest Atlantic. Over six breeding seasons, we used a combination of Global Positioning System and Global Location Sensor devices to measure characteristics of individual foraging trips during the incubation period. Females travelled significantly greater distances and went farther from the breeding colony than did males on individual foraging trips. For both sexes, the longer the foraging trip, the greater the distance. Independent of trip duration, females travelled farther, and spent a greater proportion of their foraging trips prospecting widely as defined by behavioural categories derived from a Hidden Markov Model. For both sexes, trip duration decreased with date. Sex differences in these foraging metrics were apparently not a consequence of morphological differences or spatial segregation. Our data are consistent with the idea that female foraging strategies differed from male foraging strategies during incubation in ways that would be expected if females were still compensating for egg formation.

Abstract Background Homeothermic marine animals in Polar Regions face an energetic bottleneck in winter. The challenges of short days and cold temperatures are exacerbated for flying seabirds with small body size and limited fat stores. We use biologging approaches to examine how habitat, weather, and moon illumination influence behaviour and energetics of a marine bird species, thick-billed murres (Uria lomvia). Methods We used temperature-depth-light recorders to examine strategies murres use to survive winter in the Northwest Atlantic, where contrasting currents create two distinct marine habitats: cold (−0.1 ± 1.2 °C), shallower water along the Labrador Shelf and warmer (3.1 ± 0.3 °C), deep water in the Labrador Basin. Results In the cold shelf water, murres used a high-energy strategy, with more flying and less diving each day, resulting in high daily energy expenditure and also high apparent energy intake; this strategy was most evident in early winter when day lengths were shortest. By contrast, murres in warmer basin water employed a low-energy strategy, with less time flying and more time diving under low light conditions (nautical twilight and night). In warmer basin water, murres increased diving at night when the moon was more illuminated, likely taking advantage of diel vertically migrating prey. In warmer basin water, murres dove more at night and foraging efficiency increased under negative North Atlantic Oscillation (calmer ocean conditions). Conclusions The proximity of two distinct marine habitats in this region allows individuals from a single species to use dual (low-energy/high-energy) strategies to overcome winter energy bottlenecks.