Seabirds are long-lived apex predators that serve as key sentinels of ocean health, integrating contaminant exposure across trophic levels. This systematic review synthesises 275 peer-reviewed studies on biomarkers of aquatic contamination in seabirds, with 124 (45.1%) published in the last decade and the earliest dating back to 1976. Most studies focused on biomarkers associated with organic contaminants (64.0%), metal(loid)s (19.6%), or both (8.0%). Blood was the predominant biological matrix (55.6%), reflecting its suitability for non-lethal monitoring, followed by liver tissue (40.7%), primarily used to assess detoxification pathways. Unlike previous reviews that focused exclusively on molecular biomarkers or synthesised the use of biomarkers across broad aquatic taxa, this study provides the first global, cross-disciplinary synthesis integrating biochemical, cellular, molecular and physiological biomarkers specifically in seabirds. Across the dataset, biomarkers of xenobiotic biotransformation were the most frequently investigated (32.0% of studies), followed by endocrine disruption (20.3%) and oxidative stress (14.9%). A key gap identified was the limited application of biomarkers in the Southern Hemisphere species. Results highlighted the need to incorporate omics approaches, such as transcriptomics and proteomics to improve understanding of sublethal toxicity of aquatic contaminants. Coupling these approaches with non-lethal sampling in ecologically diverse sentinel species and mapping of global contamination hotspots offers a path toward developing sensitive, reproducible indicators of marine environmental health. Collectively, these findings provide an evidence-based framework to guide monitoring programmes and targeted capacity building in underrepresented regions, strengthening transboundary assessment of contaminants impacts and regulatory actions in marine ecosystems.

Herons are predators at high levels of the trophic webs in aquatic and adjacent terrestrial environments. They often breed sympatrically, forming colonies with multiple species that play key roles in the transport of nutrients and can serve as environmental sentinels. However, studies evaluating foraging habits, resource partitioning, and niche overlap are still scarce. We used complementary stable isotopes of carbon and nitrogen, and food remains analyses to investigate diet overlap among cattle egret (Bubulcus ibis), snowy egret (Egretta thula), and black-crowned night heron (Nycticorax nycticorax) at the Lagoa dos Patos estuary, southern Brazil. These species fed on vertebrates (mainly fish but also anurans and bird chicks) and arthropods (insects, arachnids, and crustaceans) in varying proportions. Similarly, stable isotopes demonstrated assimilated sources from estuarine, limnetic, and terrestrial areas, with food items differing in proportions. The diet of cattle egrets was composed mainly of terrestrial prey, while snowy egrets fed mainly on aquatic prey. Black-crowned night herons had a generalist diet and the highest isotopic niche breadth, which overlapped with other species. Our study demonstrated that small-to-medium-sized herons have trophic plasticity and despite sharing food items in different proportions, they show a distinction in at least one of the niche dimensions (temporal, spatial, or trophic), which allows for the coexistence of sympatric species in multispecies colonies.

Seabird diets serve as valuable tools for monitoring forage fish populations, particularly when fishery-dependent data overlook key segments such as juvenile cohorts. In this study, we evaluated whether Peruvian booby (Sula variegata), a predator of anchoveta (Engraulis ringens), could be used as an ecological indicator of anchoveta size structures during the early industrial fishing season in northern Peru. We analysed regurgitated prey samples derived from tagged birds in combination with GPS tracking, bird-borne video footage, and official fishery landing and effort data. Anchoveta length distributions in booby diets revealed a high proportion of juveniles (< 12 cm), which were significantly underrepresented in concurrent fishery landings. Despite occasional interactions with fishing vessels, the size of the prey consumed did not differ significantly with the vessel presence status, suggesting that boobies forage largely independently of the industrial fleet. Our findings are consistent with other studies that have shown that seabirds effectively track fish recruitment dynamics through their diets. Additionally, the spatial segregation of anchoveta, with juveniles being inshore and adults being offshore, may explain the discrepancies between seabird and fishery size data. These results underscore the utility of the Peruvian booby as a sentinel species for detecting early recruitment signals in anchoveta populations. We propose that systematic seabird diet monitoring, particularly at the beginning of the fishing season, can provide complementary insights into fish population structures and strengthen ecosystem-based fishery management, especially in data-limited or logistically constrained settings.

Mercury (Hg) is a toxic contaminant, which poses serious threats to both wildlife and humans worldwide. Although tropical oceans receive half of the world's atmospheric Hg depositions, its biomonitoring is largely overlooked in these ecosystems. This study provides a comprehensive, pantropical assessment of Hg contamination of marine ecosystems, using the sooty tern (Onychoprion fuscatus) as bioindicator. Total Hg concentrations were measured from feathers collected in 28 colonies across all tropical oceans (2003-2022), from adults (n = 564) and chicks (n = 407), to evaluate longer- and shorter-term contamination. To investigate the role of bird trophic ecology on Hg contamination, bulk stable isotopes of carbon (δ13C) and nitrogen (δ15N) were also analysed, as respective proxies for feeding habitat and diet. Because baselines of stable isotopes may vary at large spatial scales, compound-specific nitrogen stable isotope analyses of amino-acids were performed on a subset of adults (n = 91, 19 colonies), to calculate their trophic position (TP), accounting for both baseline and trophic effects. As expected, Hg concentrations were higher in adults than chicks, because of their shorter bioaccumulation period. Overall, colonies from the Northern Hemisphere exhibited the highest Hg concentrations, consistently with higher historical anthropogenic emissions of Hg in the North. Models revealed that Hg contamination was driven by environmental contamination (colony location, feeding habitat) rather than diet (TP), which remained similar across the pantropical range. Our findings provide important baseline data for tropical marine ecosystems and underscore the need for enhanced monitoring in regions, where gold-mining and changing oceanographic conditions will likely modify future Hg exposure.

ABSTRACT Dispersal is the process of movement of organisms among habitats across the landscape, and passive dispersal occurs when the transport of organisms or their propagules is mediated by vectors. Research on the role of waterbirds in the dispersal of microalgae through epizoochory and endozoochory remains scarce. We evaluated the ability of a large‐bodied, resident Neotropical waterbird species, the southern screamer ( Chauna torquata ), to disperse microalgae through both epi‐ and endozoochory in Neotropical wetlands. The study was conducted in a Ramsar Site located in the southernmost region of Brazil. Microalgal samples were collected from a natural wetland for reference, from two body regions (toes and feathers) of five adult birds, and from 15 fresh faecal samples of the species. All samples were collected in the same locality and during the cold season. A total of 92 microalgal taxa were recorded in the wetland, while 61 taxa and 154 individuals were found on the toes, 44 taxa and 93 individuals on the feathers, and 18 taxa and 194 individuals in faeces. Microalgal richness differed among the wetland, toes, feathers, and faeces, with the highest richness observed in the wetland. Richness observed on the toes and feathers was higher than that in faeces, whereas richness did not differ between toes and feathers. Pairwise comparisons revealed that the composition of microalgae found in faeces differed significantly from that found in the wetland, toes, and feathers. Our findings demonstrate that southern screamer has a strong potential to disperse microalgae through both epizoochory and endozoochory, although each pathway operates under distinct selective filters. This study highlights the importance of waterbirds in maintaining microalgal connectivity across wetland ecosystems.

Marine and freshwater pollution is a major environmental concern, yet the spatial extent of estuarine contamination in marine food webs remains poorly understood. In this study, we sampled blood from piscivorous waterbirds (15 species, 316 individuals) along a gradient from estuaries in southeastern Brazil to the nearshore and offshore southwestern Atlantic Ocean to assess trace element concentrations and the influence of habitat and trophic position on the basis of stable isotopes of carbon, nitrogen, and sulfur. All nonessential trace elements (arsenic, cadmium, lead, and mercury) were inversely related to sulfur isotope values (δ34S) and decreased along the estuarine-open ocean gradient. Conversely, most essential elements (chromium, copper, and manganese) were positively correlated with δ34S, suggesting an increase from estuarine to oceanic waters. Nonessential trace elements in estuarine birds were above the benchmarks of toxicity established for bird species, suggesting potential health impairment due to trace element contamination associated with freshwater inputs. In addition, the lower concentrations of essential elements in estuarine birds may suggest interference in metal homeostasis caused by high concentrations of nonessential elements. Assessments combining multiple trace elements and stable isotopes, particularly sulfur, remain rare over large spatial scales. Across this broad environmental gradient, stable sulfur isotopes proved to be efficient markers of bird habitats for assessing spatial patterns in trace element contamination in aquatic food webs.

Abstract Recent advances in biologging have led to the widespread use of accelerometers, which generate high‐resolution movement data essential for understanding animal behaviour. Derived from tri‐axial accelerometry, Overall Dynamic Body Acceleration (ODBA) serves as a proxy for energy expenditure that is less invasive and more cost‐effective than alternative methods, contributing to a better understanding of individual survival and population dynamics. However, many long‐term datasets lack accelerometry due to limitations in instrumentation or older technologies, thereby constraining their utility in multi‐year ecological studies. Marine top predators, particularly seabirds, are valuable ecosystem sentinels due to their foraging strategies, energy constraints and sensitivity to environmental conditions. Understanding energy use during at‐sea travel is essential for forecasting colony viability under climate change, thus supporting long‐term ecological research and conservation efforts. High‐resolution biologging has facilitated data‐driven approaches to monitor seabird behaviour, but gaps in accelerometry data remain a challenge. New developments in deep neural networks (DNNs) offer opportunities to reconstruct missing biologging‐derived metrics by capturing the complex spatiotemporal relationships between movement and environmental data. One way to model such dependencies is to use a transformer architecture, which processes all inputs jointly and produces representations that explicitly encode relationships between them. In this study, we present ODBAFormer, a transformer‐based model designed to infer ODBA from GPS trajectories and environmental covariates. We applied ODBAFormer to seabird tracking data to address gaps in proxy data for energy expenditure. We evaluated the model on unseen data and compared it with state‐of‐the‐art machine‐learning regression method XGBoost as a baseline. We also explored its sensitivity to data heterogeneity and different environmental covariates combinations. Overall, ODBAFormer accurately reconstructs ODBA time series and proxies for both energy budgets and spatial energy expenditure distribution, providing a scalable solution to enrich legacy datasets or for situations where the use of multisensor loggers is limited by cost or weight.

Understanding tropical seabird foraging strategies is essential for evaluating ecosystem functioning within Very Large Marine Protected Areas (VLMPAs). We investigated spatial and trophic behavior of brown booby (Sula leucogaster) at the Saint Peter and Saint Paul Archipelago (SPSP), a remote breeding site within a VLMPA in the equatorial Atlantic Ocean. Using GPS tracking from 207 individuals (706 trips, 2014–2015 and 2023–2024), stable isotopes (δ13C and δ15N) from 58 blood samples, and 49 regurgitated samples, we assessed variation in foraging effort and diet across sex, breeding stage, and temporal scales. Despite pronounced reversed sexual size dimorphism, no intersexual differences were detected in movement parameters. However, females exhibited significantly higher δ15N values, indicating subtle trophic segregation. Breeding stage showed minimal influence, suggesting that extreme nest density and continuous territorial defense override intrinsic reproductive demands. Pronounced interannual variation in foraging effort was detected, with 2023 showing nearly double the ranges compared to 2015. Seasonally, trip metrics did not differ, but time allocation shifted between austral winter and summer: traveling decreased (48.1

Highways can alter the foraging behavior of top predators, such as raptors, by providing carcasses and attracting prey associated with human-modified environments or in areas preserved by set-aside areas along roads. However, exploiting these resources near roads increases the risk of collisions and poses additional conservation challenges. Here, we investigated the diet and individual specialization of Great Horned Owls (Bubo virginianus, n = 26) killed on highways in southern Brazil, integrating stomach content analysis with carbon and nitrogen stable isotope analysis (SIA) from multiple tissues. The species exhibited generalist feeding habits at the population level, with mammals (Prey-Specific Relative Importance Index, PSIRI% = 35.7) and insects (PSIRI% = 20.8) as the main prey items identified in stomach contents. SIA indicated a predominant assimilation of mammals in muscle (95% Credible Intervals CI = 20.4–48.2%), liver (95% CI = 25.9–58.4%), and feathers (95% CI = 30.7–60.2%), followed by amphibians (muscle: 95% CI = 3.5–38.9%; liver: 95% CI = 3.2–45.4%; feathers: 95% CI = 2.8–44.8%). Isotopic data also revealed high individual specialization, particularly reflected by carbon isotopic variation, suggesting consistent consumption of different prey groups or prey mixtures among individuals. Such specialization may lead to differential exposure to roadkill risk in anthropogenic landscapes, both by feeding on carcasses or preying in set-aside areas along roads. The integration of traditional dietary and isotopic approaches, unprecedented for this species, provides novel insights into the trophic ecology of the Great Horned Owl in highway-fragmented ecosystems of southern Brazil and underscores the importance of considering intraspecific variability in ecological and conservation studies.

Migratory species may influence structural components of species assemblages, such as biomass and diversity patterns. A total of 10 ship-based, strip-transect seabird surveys were undertaken in all seasons (2019-2024) off the northeast coast of Northland, Aotearoa/New Zealand. Almost all seabird species recorded were migratory or wide-ranging dispersive (23 of 25). Multivariate model-based ordinations revealed that season primarily explained species assemblages, while including environmental variables such as sea surface temperature and chlorophyll-a (useful proxies for studying seabird distribution) offered little extra explanatory power at the assemblage level. There was no clear spatial pattern in the assemblages, suggesting that the study area was used uniformly by the species present at the time. The total seabird biomass present was strongly influenced by the seasonal occurrence of four medium-sized, migratory procellariiforms: ta & strns;iko (black petrel; Procellaria parkinsoni), rako (Buller's shearwater; Ardenna bulleri), o & strns;i (grey-faced petrel; Pterodroma gouldi) and toanui (flesh-footed shearwater; Ardenna carneipes). The biomass estimates showed an eight-fold increase from winter (243 kg/km2) to summer (1885 kg/km2). Northland will likely be the first region in Aotearoa/New Zealand to experience the consequences of oceanic warming. The study establishes a baseline against which to measure potential future changes in seabird occurrences. Based on descriptive and modelling approaches, the study demonstrated the role of species' phenologies in shaping assemblages of seabird species and their impact on total estimated biomass, which may affect ecosystem functioning and energy fluxes.

Abstract Realistic simulation of animal movement is fundamental to conservation, habitat modeling, and ecological scenario evaluation. Traditional approaches struggle to capture multi-scale trajectory dynamics, while generative deep learning for complete trajectory simulation remains largely unexplored in ecology due to data scarcity. We show that a diffusion model pre-trained on millions of vehicle GPS trajectories can be fine-tuned on hundreds of seabird central-place foraging trips to simultaneously generate ecologically realistic trajectories for five species and six breeding colonies. The fine-tuned model consistently outperforms four state-of-the-art baselines (GAN, VAE, HMM, iSSF) across movement metrics spanning step dynamics, spatial distribution, and behavioral temporality, with comparable or shorter computation times. Domain transfer reaches full performance in 35 minutes versus 7 hours from scratch, and conditioning on species and colony enables generalization to unseen combinations from as few as 10 trajectories. These results establish cross-domain transfer learning as a new paradigm for data-efficient generative animal movement modeling.

Seabirds are highly mobile organisms but often exhibit philopatric behavior, with each colony potentially forming a distinct breeding unit, leading to genetic structuring. Molecular markers are valuable tools for detecting genetic distinctiveness and supporting conservation strategies. The pantropical red-footed booby (Sula sula) nests in trees and currently has a single breeding site in the southwestern Atlantic Ocean at the Fernando de Noronha Archipelago, Brazil. The species was extirpated from Trindade Island, 1200 km off the Brazilian coast, due to forest destruction, and is now classified as “Endangered” in Brazil. This study compared the genetic structure and diversity between the extinct Trindade population and the extant Noronha population. Blood samples from Noronha and interdigital membrane samples from museum specimens from Trindade were analyzed using microsatellite markers. The Trindade population exhibited greater genetic diversity than Noronha, holding exclusive alleles. Additionally, the two colonies shared ancestry, with subtle signs of genetic segregation. This ancestry may be related to gene flow and a founder effect from Trindade individuals in the Noronha population. Ultimately, the extinction of the Trindade population led to the loss of a different genetic profile and reduced genetic diversity of red-footed boobies in the southwestern Atlantic Ocean. These findings highlight the importance of investigating evolutionary processes and dynamics within species for assessing anthropogenic impacts on biodiversity and conservation. Translocating red-footed boobies to Trindade Island could restore its ecological function and potentially prevent the imminent extinction of two endemic frigatebird species, which nest on trees and are kleptoparasitic on boobies.

Understanding the relationships between organisms and their environment is crucial to determining important areas for conservation and monitoring. In rapidly changing oceans, one approach to quantify these relationships is to identify species assemblages. This study used a nine year dataset of seabird observations sampled approximately every two months during a cross-shelf transect to describe assemblages at the Subtropical Frontal Zone, in southeast Aotearoa/New Zealand. During 36 voyages, 47 species and a minimum of 69,025 individual birds were recorded. We used multivariate, model-based ordinations to identify assemblages against spatial (distance from the coast), temporal (season) and environmental (water mass) predictors. The multivariate models suggest that the distance from the coast and seasons explain most of the observed variability. Gulls and shags influenced a coastal assemblage (<25 km from the coast), and most albatrosses and petrels were only recorded offshore (>35 km). Seasons strongly influenced the assemblages, with 31 of the 39 analysed species classified as migratory or dispersive. Over the nine year dataset, the probability of occurrence of nearly 40% of the analysed species changed, indicating possible changes in the assemblage structure and species' ranges. This study shows the importance of accounting for seasonality when describing assemblages in regions supporting high proportions of migratory and/or wide-ranging species. The observed changes in the probability of occurrence of several species may be the first evidence for the effects of oceanographic changes recently described for the southwest Pacific Ocean due to above-average warming caused by climate change.

Population abundance and trend estimates are crucial to science, management, and conservation. Shorebirds, which are abundant in many coastal habitats and play important roles in coastal ecosystems, are facing some of the most dramatic population declines of any group of birds globally. However, accurate and up-to-date population estimates are lacking for most shorebird species. We thus conducted large-scale, simultaneous, and community scientist-led surveys of the Atlantic Coast of southern South America, stretching from central Brazil to Tierra del Fuego, to gather counts of shorebirds stratified by habitat that we combined with remote sensing analyses and two-step hurdle models that accounted for presence and abundance. Our objectives were to estimate shorebird densities by habitat, identify high-concentration areas, understand the environmental factors affecting their distributions, and provide population estimates for both Nearctic and Neotropical species. We counted a total of 37,207 shorebirds of 17 species and, from those counts, estimated that nearly 1.1 million shorebirds use the region's coastline. We found that the northern portion of the region was important for sandy beach specialists, while southern portions supported higher abundances of species that rely on intertidal mudflat and rocky habitats. We also found that shorebirds occurred in the highest densities in wetland habitats and that fewer shorebirds occupied areas that were further away from estuaries. Although not directly comparable, our results suggest the population sizes of the Nearctic species whose nonbreeding ranges are predominantly in southern South America may have declined substantially since previous estimates. At the same time, our study represents the first empirically derived population estimates for Neotropical breeding shorebird species and indicates that they are far more abundant than previously thought. Taken together, our results highlight the power of community scientists to carry out structured protocols at continental scales and generate critical data for a group of at-risk species.