Seabirds are frequently infected by avian influenza virus (AIV), which prior to 2021 primarily consisted of low-pathogenic AIV with limited reports of disease during infection. However, since highly pathogenic AIV (HPAIV) H5N1 clade 2.3.4.4b was introduced to North America in late 2021, HPAIV outbreaks in seabirds have occurred in multiple regions, with high levels of morbidity and mortality in many species. While monitoring active viral infections is critical for tracking disease burden, monitoring prior viral exposure via antibody detection in species that experienced large outbreaks is important for identifying individual- and population-level impacts of AIV on immunity and survival. We capitalized on ongoing egg collection programmes to assess the prevalence of antibodies against AIV nucleoprotein (NP) and hemagglutinin subtype 5 (H5) in 523 eggs collected in 2022 and 2023 from 11 seabird species that breed in the northwestern Atlantic, including primarily samples from eastern Canada and two from western Iceland. The prevalence of AIV antibodies in eggs varied across regions, species and years. American common eider (Somateria mollissima dresseri) eggs had the highest AIV antibody prevalence compared to sympatric species in 2023. Longitudinal samples were available for northern gannets (Morus bassanus) and American herring gulls (Larus argentatus smithsoniansus) at several sites, where the prevalence of anti-NP and anti-H5 antibodies increased from 2022 to 2023. Examining AIV antibody prevalence in seabird eggs can be a useful tool to investigate population-level AIV exposure, while we acknowledge our limited understanding of differential antibody waning rates and the relationship between titre and susceptibility.

Seabirds are one of the most at-risk avian groups worldwide, and incidental catch in fishing practices is one of the top threats for seabirds globally. Seabirds that forage on fish through surface feeding, pursuit-diving, or plunge-diving are particularly vulnerable to bycatch. Bycatch mitigation solutions are therefore a vital component of global seabird conservation, but owing to the episodic nature of bycatch and its involvement of match-mismatch contingencies, results from existing efforts involving gear additions (e.g., lights, flags, or buoys) are highly varied and, at times, reduce target catch. Altering the time during which gear remains in the water and modifying fishing practices based on the activity patterns of target fish and seabirds is a promising option for bycatch mitigation. We experimentally tested best practices for the soak timing and duration of shallow-set gillnets used in the Atlantic herring ( Clupea harengus ) bait fishery in Newfoundland and Labrador, Canada. We compared catch, bycatch, and seabird activity among control (ca. 24 h) and short (ca. 12 h) set durations that were left to soak overnight or only during daylight hours. Target catch did not differ between control and short overnight sets but was greatly reduced during short daytime sets. Nearly all bycatch, including all seabird bycatch, occurred during the control sets. Seabirds associated with fishing vessels throughout the day. Since the catch of herring in gillnets occurs at night outside of most coastal seabirds’ foraging period, we recommend that fishers continue to haul their nets early every morning to minimize the time where shallow-set nets are filled with prey during daytime hours, thereby limiting seabird bycatch risk.

Fishing technologies often exploit the visual sensitivity of target species to alter their behaviours. Atlantic cod (Gadus morhua Linnaeus, 1758) are an economically important species, commonly targeted by fisheries in the North Atlantic, yet the behaviour of adult Atlantic cod in reaction to the simultaneous presentation of various light stimuli has not been assessed in an isolated setting to determine if there is a preference for certain light qualities. To assess the influence that artificial light may have on the behaviour of Atlantic cod, we investigated the movement of wild-caught cod in a laboratory setting with green, blue, and white light with a blank control presented in paired choice tests. We predicted that green light would have the greatest influence on cod behaviour and that they would preferentially spend more time in proximity to that light condition. The findings show that cod behaved consistently across trials and across experimental sessions, and that the right side of the arena was preferred regardless of the colours of light presented. These findings indicate that cod do not prefer to spend more time in proximity to certain colours of light in an artificial environment, which has direct implications for animal husbandry, fisheries research, and behavioural ecology.

Highly pathogenic avian influenza (HPAI) H5N1 caused mass mortality of wildlife across the North Atlantic in 2022. Following European outbreaks, the first North American case was detected on the island of Newfoundland, Canada in November 2021, before spreading throughout North America. During the following summer, Newfoundland and surrounding islands (NFLD) experienced one of the most significant mortalities in Canadian provinces, with seabirds being the most affected taxa. From surveys and citizen reports, we estimate that 13 517 mortalities that can be attributed to HPAI occurred in NFLD from April to September 2022. Most estimated mortalities were among Northern Gannets (Morus bassanus (Linnaeus, 1758)) (6596), Common Murres (Uria aalge (Pontoppidan, 1763)) (5992), Atlantic Puffins (Fratercula arctica (Linnaeus, 1758)) (282), and Black-legged Kittiwakes (Rissa tridactyla (Linnaeus, 1758)) (217). Mortality reports moved from west to east along the southern, then eastern NFLD coast, and peaked in July and August. We formulated exploratory hypotheses regarding traits that could contribute to infection and mortality. Species differences in mortality most strongly associated with inter-nest distance, breeding phenology, and at-sea overlap with allospecifics from other colonies. Unprecedented seabird mortality and ongoing transmission within the circulating avian influenza viruses highlight the need for continued monitoring and development of conservation strategies.

Density-dependent competition for food influences the foraging behaviour and demography of colonial animals, but how this influence varies across a species’ latitudinal range is poorly understood. Here we used satellite tracking from 21 Northern Gannet Morus bassanus colonies (39% of colonies worldwide, supporting 73% of the global population) during chick-rearing to test how foraging trip characteristics (distance and duration) covary with colony size (138–60 953 breeding pairs) and latitude across 89% of their latitudinal range (46.81–71.23° N). Tracking data for 1118 individuals showed that foraging trip duration and maximum distance both increased with square-root colony size. Foraging effort also varied between years for the same colony, consistent with a link to environmental variability. Trip duration and maximum distance also decreased with latitude, after controlling for colony size. Our results are consistent with density-dependent reduction in prey availability influencing colony size and reveal reduced competition at the poleward range margin. This provides a mechanism for rapid population growth at northern colonies and, therefore, a poleward shift in response to environmental change. Further work is required to understand when and how colonial animals deplete nearby prey, along with the positive and negative effects of social foraging behaviour.

Little is known about the spatial and dietary overlap of seabird species during the non-breeding season, when scarce and patchy marine food resources could lead to interspecific competition. We aimed to quantify spatiotemporal and isotopic niche overlap among common murres Uria aalge, razorbills Alca torda, and Atlantic puffins Fratercula arctica outside the breeding season by combining data from geolocators and stable isotope ratios (delta 15N, delta 13C) of belly, secondary, and head feathers collected in 2017-2020 from birds breeding in coastal northeastern Newfoundland, Canada. Seasonal utilization distributions of each species indicated generally low spatial overlap during most of the non-breeding period, with exceptions immediately post-breeding and with variability in movement paths among puffins. Stable isotope analysis revealed a broader isotopic niche (1.5 to 3x) for puffins than other species, matching their greater spatial variation. There was no isotopic niche overlap among the 3 species, except during flight feather molt of razorbills and murres. Individual puffins located in the same area as razorbills or murres had lower delta 15N values, suggesting a lower trophic position. The minimal overlap of these 3 alcid species during an understudied phase of their annual cycle suggests that they segregate spatially and partition resources, implying that different spatial planning and ecosystem conservation strategies should be applied to each of these 3 species.

ABSTRACT Following the detection of novel highly pathogenic avian influenza virus (HPAIV) H5N1 clade 2.3.4.4b in Newfoundland, Canada, in late 2021, avian influenza virus (AIV) surveillance in wild birds was scaled up across Canada. Herein, we present the results of Canada’s Interagency Surveillance Program for Avian Influenza in Wild Birds during the first year (November 2021–November 2022) following the incursions of HPAIV from Eurasia. The key objectives of the surveillance program were to (i) identify the presence, distribution, and spread of HPAIV and other AIVs; (ii) identify wild bird morbidity and mortality associated with HPAIV; (iii) identify the range of wild bird species infected by HPAIV; and (iv) genetically characterize detected AIV. A total of 6,246 sick and dead wild birds were tested, of which 27.4% were HPAIV positive across 12 taxonomic orders and 80 species. Geographically, HPAIV detections occurred in all Canadian provinces and territories, with the highest numbers in the Atlantic and Central Flyways. Temporally, peak detections differed across flyways, though the national peak occurred in April 2022. In an additional 11,295 asymptomatic harvested or live-captured wild birds, 5.2% were HPAIV positive across 3 taxonomic orders and 19 species. Whole-genome sequencing identified HPAIV of Eurasian origin as most prevalent in the Atlantic Flyway, along with multiple reassortants of mixed Eurasian and North American origins distributed across Canada, with moderate structuring at the flyway scale. Wild birds were victims and reservoirs of HPAIV H5N1 2.3.4.4b, underscoring the importance of surveillance encompassing samples from sick and dead, as well as live and harvested birds, to provide insights into the dynamics and potential impacts of the HPAIV H5N1 outbreak. This dramatic shift in the presence and distribution of HPAIV in wild birds in Canada highlights a need for sustained investment in wild bird surveillance and collaboration across interagency partners. IMPORTANCE We present the results of Canada’s Interagency Surveillance Program for Avian Influenza in Wild Birds in the year following the first detection of highly pathogenic avian influenza virus (HPAIV) H5N1 on the continent. The surveillance program tested over 17,000 wild birds, both sick and apparently healthy, which revealed spatiotemporal and taxonomic patterns in HPAIV prevalence and mortality across Canada. The significant shift in the presence and distribution of HPAIV in Canada’s wild birds underscores the need for sustained investment in wild bird surveillance and collaboration across One Health partners.

In 2022, highly pathogenic avian influenza (HPAI) virus resulted in mass mortality throughout seabird colonies in the North Atlantic Ocean. While mortalities and transmission of the virus are being documented, other effects are less understood. We documented nest abandonment and unprecedented reproductive failure by Northern Gannets Morus bassanus at Cape St. Mary's, Newfoundland and Labrador, Canada, the species' southernmost colony. Reproductive success in 2022 was the lowest on record at 17%, which was likely a result of adults abandoning the nest and succumbing to avian influenza virus (AIV) infection. Following the AIV outbreak at Cape St. Mary's, we also documented extremely long foraging trips, including the second known instance of inter-colony movement by an adult Northern Gannet, who embarked on two trips to the gannet colony on Baccalieu Island. This inter-colony movement represents a possible means of viral transmission between colonies. The effects of HPAI may have been exacerbated as a result of heat stress during a marine heatwave, which coincided with the major outbreak at this colony. As this HPAI virus could continue to circulate in seabirds, ongoing monitoring of mortality and other indirect effects of AIV outbreaks are needed to inform future impacts.

Mercury (Hg) is a metallic trace element toxic for humans and wildlife that can originate from natural and anthropic sources. Hg spatial gradients have been found in seabirds from the Arctic and other oceans, suggesting contrasting toxicity risks across regions. Selenium (Se) plays a protective role against Hg toxicity, but its spatial distribution has been much less investigated than that of Hg. From 2015 to 2017, we measured spatial co-exposure of Hg and Se in blood samples of two seabird species, the Brünnich's guillemot (Uria lomvia) and the black-legged kittiwake (Rissa tridactyla) from 17 colonies in the Arctic and subarctic regions, and we calculated their molar ratios (Se:Hg), as a measure of Hg sequestration by Se and, therefore, of Hg exposure risk. We also evaluated concentration differences between species and ocean basins (Pacific-Arctic and Atlantic-Arctic), and examined the influence of trophic ecology on Hg and Se concentrations using nitrogen and carbon stable isotopes. In the Atlantic-Arctic ocean, we found a negative west-to-east gradient of Hg and Se for guillemots, and a positive west-to-east gradient of Se for kittiwakes, suggesting that these species are better protected from Hg toxicity in the European Arctic. Differences in Se gradients between species suggest that they do not follow environmental Se spatial variations. This, together with the absence of a general pattern for isotopes influence on trace element concentrations, could be due to foraging ecology differences between species. In both oceans, the two species showed similar Hg concentrations, but guillemots showed lower Se concentrations and Se:Hg than kittiwakes, suggesting a higher Hg toxicity risk in guillemots. Within species, neither Hg, nor Se or Se:Hg differed between both oceans. Our study highlights the importance of considering Se together with Hg, along with different species and regions, when evaluating Hg toxic effects on marine predators in international monitoring programs.

CapsuleH5N1 clade 2.3.4.4b viruses have caused significant mortality events in various wild bird species across Europe, North America, South America, and Africa. In North America, the largest impacts on wild birds have been in eastern Canada, where at least 40,391 wild birds were reported to have died from highly pathogenic avian influenza (HPAI) between April and September 2022.AimsTo apply previously established methods to collect and quantify the total reported wild bird mortality in eastern Canada from October 2022 to September 2023.MethodsWe documented the spatial, temporal, and taxonomic patterns of wild bird mortality in the 12 months that followed a mass mortality event in the summer of 2022, and then quantified the observed differences in mortality across the spring and summer (April to September) of 2022 and 2023. In eastern Canada, there was high uncertainty about whether 2023 would bring another year of devastating HPAI-linked mortalities.ResultsMortalities in the spring and summer of 2023 were 93% lower than in 2022, but encompassed a wider diversity of species. Mortalities in the fall/autumn and winter (non-breeding season) were dominated by waterfowl, while mortalities during the spring and summer (breeding season) were dominated by seabirds. Due to a low prevalence of HPAI among a subset of tested birds, we cannot broadly attribute the reported mortalities in 2023 to HPAI. However, our analysis did identify three notable mortality events linked to HPAI, involving at least 1646 Greater Snow Geese Anser caerulescens atlanticus, 232 Canada Geese Branta canadensis, and 212 Northern Gannets Morus bassanus. The latter reflected the continuation of a mortality event from the Northern Gannet's 2022 breeding season.ConclusionsThis study emphasizes the ongoing need for H5Nx surveillance and mortality assessments as the patterns of mortality in wild populations continue to change.

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.

Seabird colonies with long-term monitoring records, i.e., > 50 years, are rare. The population data for northern gannets (Morus bassanus) in Cape St. Mary’s (CSM) Ecological Reserve (Newfoundland and Labrador, Canada) is robust, extending back to 1883 when the colony was presumed established. We inferred the colony’s historical population shifts by measuring ornithogenic proxies in a dated sediment record collected from a nearby pond. Our record extended to the early eighteenth century, but the proxy data only began to show significant signs of seabird presence between ca. 1832 and 1910, aligning with the period gannets were first observed at CSM. Through the twentieth century, we observed significant increases in δ15N, P, Zn, Cd, and chlorophyll a, coeval with a shift in the dominant diatom species, indicating rapid colony growth. The proxies were overall highest in ca. 2005, corresponding to the reported historical maximum of the gannet colony in 2009. Our results validate that paleo-reconstructions using ornithogenic proxies can accurately reflect population trends and provide a stronger understanding of the colony’s establishment and growth. This study highlights the value of applying paleolimnological methods in seabird population studies to frame the history of a colony’s dynamics and inform conservation efforts.

In 2022, a severe outbreak of disease caused by clade 2.3.4.4b Highly Pathogenic Avian Influenza (HPAI) H5N1 virus resulted in unprecedented mortality among wild birds in eastern Canada. Tens of thousands of birds were reported sick or dead, prompting a comprehensive assessment of mortality spanning the breeding season between April 1 and September 30, 2022. Mortality reports were collated from federal, Indigenous, provincial, and municipal agencies, the Canadian Wildlife Health Cooperative, and other nongovernmental organizations, universities, and citizen science platforms. A scenario analysis was conducted to refine mortality estimates, accounting for potential double counts from multiple sources under a range of spatial and temporal overlaps. Correcting for double counting, HPAI is estimated to have caused 40,391 wild bird mortalities in eastern Canada during the spring and summer of 2022; however, this figure underestimates total mortality as it excludes unreported deaths on land and at sea. Seabirds and sea ducks, long-lived species that are slow to recover from perturbations, accounted for 98.7% of estimated mortalities. Our study provides estimates of bird mortality, with Northern Gannets (Morus bassanus; 25,669), Common Murres (Uria aalge; 8133), and American Common Eiders (Somateria mollissima dresseri; 1894) exhibiting the highest mortality figures. We then compare these mortality estimates with recent population estimates and trends and make an initial assessment of whether biologically meaningful population-level impacts are possible. Specifically, we focus on the Northern Gannet, a species that has suffered significant global mortality, and two harvested species, Common Murre and American Common Eider, to inform management decisions. Our analysis suggests population-level impacts in eastern Canada are possible for Northern Gannets and American Common Eiders, but are unlikely for Common Murres. This study demonstrates a comprehensive approach to assessing mortality and underscores the urgent need for further research to understand the broader ecological ramifications of the HPAI outbreak on wild bird populations.

During 2021 and 2022 High Pathogenicity Avian Influenza (HPAI) killed thousands of wild birds across Europe and North America, suggesting a change in infection dynamics and a shift to new hosts, including seabirds. Northern Gannets Morus bassanus appeared to be especially severely impacted, but a detailed account of the data available is required to help understand how the HPAI virus (HPAIV) spread across the meta-population, and the ensuing demographic consequences. Accordingly, we analyse information on confirmed and suspected HPAIV outbreaks across most North Atlantic Gannet colonies and, for the largest colony (Bass Rock, UK), provide impacts on population size, breeding success, and preliminary results on apparent adult survival and serology. Unusually high numbers of dead Gannets were first noted at colonies in Iceland during April 2022. Outbreaks in May occurred in many Scottish colonies, followed by colonies in Canada, Germany and Norway. By the end of June, outbreaks had occurred in colonies in Canada and the English Channel. Outbreaks in 12 UK and Ireland colonies appeared to follow a clockwise pattern with the last infected colonies recorded in late August/September. Unusually high mortality was recorded at 40 colonies (75% of global total colonies). Dead birds testing positive for HPAIV H5N1 were associated with 58% of these colonies. At Bass Rock, the number of occupied nest-sites decreased by at least 71%, breeding success declined by c. 66% compared with the long-term UK mean and the resighting of marked individuals suggested that apparent adult survival between 2021 and 2022 could have been substantially lower than the preceding 10-year average. Serological investigation detected antibodies specific to H5 in apparently healthy birds, indicating that some Gannets recover from HPAIV infection. Further, most of these recovered birds had black irises, suggestive of a phenotypic indicator of previous infection. Untangling the impacts of HPAIV infection from other challenges faced by seabirds is key to establishing effective conservation strategies for threatened seabird populations as the likelihood of further epizootics increases, due to increasing habitat loss and the industrialization of poultry production.

Artificial light at night (ALAN) is negatively impacting numerous species of nocturnally active birds. Nocturnal positive phototaxis, the movement towards ALAN, is exhibited by many marine birds and can result in stranding on land. Seabird species facing major population declines may be most at risk. Leach's Storm-Petrels (Hydrobates leucorhous) are small, threatened seabirds with an extensive breeding range in the North Atlantic and North Pacific Oceans. The Atlantic population, which represents approximately 40-48% of the global population, is declining sharply. Nocturnal positive phototaxis is considered to be a key contributing factor. The Leach's Storm-Petrel is the seabird species most often found stranded around ALAN in the North Atlantic, though there is little experimental evidence that reduction of ALAN decreases the occurrence of stranded storm-petrels. During a two-year study at a large, brightly illuminated seafood processing plant adjacent to the Leach's Storm-Petrel's largest colony, we compared the number of birds that stranded when the lights at the plant were on versus significantly reduced. We recorded survival, counted carcasses of adults and juveniles, and released any rescued individuals. Daily morning surveys revealed that reducing ALAN decreased strandings by 57.11% (95% CI: 39.29% - 83.01%) per night and night surveys revealed that reducing ALAN decreased stranding of adult birds by 11.94% (95% CI: 3.47% - 41.13%) per night. The peak stranding period occurred from 25 September to 28 October, and 94.9% of the birds found during this period were fledglings. These results provide evidence to support the implementation of widespread reduction and modification of coastal artificial light as a conservation strategy, especially during avian fledging and migration periods.

Catch efficacy and bycatch are critical factors that determine the sustainability, practicality, and profitability of fishing gears. Inshore Atlantic cod (Gadus morhua) fisheries commonly use gillnets, cod-pots, longlines and handlines. Owing to their efficiency, selectiveness, and low effort, gillnets are the most widely used gear. Gillnets however are prone to bycatch and low-quality catch. Handlines benefit from low capital investment, live high-quality fish, low bycatch, and low carbon footprint. Enhancements to handlines that could increase catch rate or size of catch would be considered beneficial and could promote uptake by harvesters using other gear types. Previous pilot research has shown that LED handline attachments that target the visual sensitivity of cod increased the catch rate of Atlantic cod. The present study builds upon this finding, incorporating three participating commercial crews and vessels. We found no significant effect of LED handline modifications on catch efficacy for Atlantic cod or bycatch. The bycatch of Atlantic wolffish (Anarhichas lupus) in our study was found to decrease with the use of green LEDs, but the data precludes complex statistical analysis. We discuss how these findings are relevant to small-scale fishers and provide an empirical reference regarding the use of such devices in the commercial fishery.

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.

Resource availability is a key factor driving marine bird movements and distributions, but direct information on prey availability is difficult to obtain at relevant scales. We present novel methods for describing multi-scale trophic associations, combining movement analyses of marine birds with estimates of forage fish surface aggregations from digital aerial survey data and species occupancy from bottom trawl survey data. We analyzed satellite telemetry data from northern gannets Morus bassanus, red-throated loons Gavia stellata, and long-tailed ducks Clangula hyemalis in the US Atlantic during the non-breeding period. Using discrete-time hidden Markov models to distinguish area-restricted (i.e. putative foraging) from transit movements, we examined how environmental factors influence movement, and how forage fish species distributions and surface aggregations influence habitat use by gannets and loons that have greater dietary reliance. Our results suggest that chlorophyll a concentration significantly affected movement behavior across species, highlighting the importance of higher-productivity areas around estuaries during colder months when regional productivity is low. Though variable across species and seasons, spatial cross-correlation analysis revealed that herring species (Family Clupeidae), including Atlantic menhaden Brevoortia tyrannus, may be important resources; it also showed positive spatial correlations with forage fish aggregations. This suggests that prey patch dynamics and factors driving aggregation formation may be as important as species composition. However, spatial patterns were generally low (<0.3), suggesting a mismatch in spatiotemporal resolution, exemplifying the challenges in quantifying trophic relationships in marine systems. Disentangling predator-prey relationships is critical to understanding the mechanisms driving marine bird behavior in rapidly changing marine systems.