Black-backed Gulls Research Articles

Different individual-level responses of great black-backed gulls (Larus marinus) to shifting local prey availability.

To grow, survive and reproduce under anthropogenic-induced changes, individuals must respond quickly and favourably to the surrounding environment. A species that feeds on a wide variety of prey types (i.e. generalist diet) may be comprised of generalist individuals, specialist individuals that feed on different prey types, or a combination of the two. If individuals within a population respond differently to an environmental change, population-level responses may not be detectable. By tracking foraging movements of great black-backed gulls (Larus marinus), a generalist species, we compared group-level and individual-level responses to an increase in prey biomass (capelin; Mallotus villosus) during the breeding season in coastal Newfoundland, Canada. As hypothesized, shifts in prey availability resulted in significantly different individual responses in foraging behaviour and space use, which was not detectable when data from individuals were combined. Some individuals maintained similar foraging areas, foraging trip characteristics (e.g., trip length, duration) and habitat use with increased capelin availability, while others shifted foraging areas and habitats resulting in either increased or decreased trip characteristics. We show that individual specialization can be non-contextual in some gulls, whereby these individuals continuously use the same feeding strategy despite significant change in prey availability conditions. Findings also indicate high response diversity among individuals to shifting prey conditions that a population- or group-level study would not have detected, emphasizing the importance of examining individual-level strategies for future diet and foraging studies on generalist species.

Annual plastic ingestion and isotopic niche patterns of two sympatric gull species at Newfoundland, Canada

Ingestion of plastic pollution by pelagic seabirds is well-documented globally, but increasingly, researchers are investigating plastic ingestion in generalist predators and scavengers like gulls. We studied the gut contents of two sympatric gull species, American herring gulls (Larus smithsoniansus) and great black-backed gulls (L. marinus), collected year-round as part of “kill-to-scare” measures at the regional sanitary landfill in St. John's, Newfoundland and Labrador, Canada, to compare ingested anthropogenic debris, trophic position and diet breadth through the year. Although great black-backed gulls fed at a higher trophic level, frequency of occurrence of plastic ingestion was similar to American herring gulls, and varied little through the year. Diet breadth (isotopic niche size) was similar between species, but American herring gulls fed at a lower trophic level during winter, perhaps indicating a change in their reliance on anthropogenic food subsidies throughout their annual cycle.

Prevalence of Antibodies to Toxoplasma gondii in Different Wild Bird Species Admitted to Rehabilitation Centres in Portugal.

Toxoplasma gondii is a worldwide zoonotic parasite. According to the “One Health” approach, studies on toxoplasmosis are essential since it affects humans and domestic and wild animals. In the present study, antibodies to T. gondii were determined in serum samples from 263 wild birds located in five wildlife rehabilitation centres in mainland Portugal by using the modified agglutination test (MAT) with a cut-off titre of 20. An overall seroprevalence of 36.5% (95% confidence interval [CI]: 30.7–42.6) was observed. For the first time, antibodies to T. gondii were detected in some avian species, including pallid swift (Apus pallidus) (33.3%), black-backed gull (Larus fuscus) (39.3%), European turtle-dove (Streptopelia turtur) (100%), bee-eater (Merops apiaster) (50.0%), carrion crow (Corvus corone) (33.3%), and Egyptian vulture (Neophron percnopterus) (100%), which expands the list of intermediate hosts of T. gondii. A lower seroprevalence was found in juvenile birds (31.9%) compared to adults (48.7%) (p = 0.016). The central region of Portugal was considered a risk factor for T. gondii infection in wild birds (odds ratio: 3.61; 95% CI: 1.09–11.91). This pioneer study calls attention to the need for further studies, to provide a clearer understanding of T. gondii epidemiology in Portugal, because it reflects wide dispersion of T. gondii oocysts in the environment.

Simultaneous GPS-tracking of parents reveals a similar parental investment within pairs, but no immediate co-adjustment on a trip-to-trip basis

BackgroundParental care benefits the offspring, but comes at a cost for each parent, which in biparental species gives rise to a conflict between partners regarding the within-pair distribution of care. Pair members could avoid exploitation by efficiently keeping track of each other’s efforts and coordinating their efforts. Parents may, therefore, space their presence at the nest, which could also allow for permanent protection of the offspring. Additionally, they may respond to their partner’s previous investment by co-adjusting their efforts on a trip-to-trip basis, resulting in overall similar parental activities within pairs.MethodsWe investigated the coordination of parental care measured as nest attendance and foraging effort in the Lesser black-backed gull (Larus fuscus), a species with long nest bouts that performs extended foraging trips out of sight of their partner. This was achieved by GPS-tracking both pair members simultaneously during the entire chick rearing period.ResultsWe found that the timing of foraging trips (and hence nest attendance) was coordinated within gull pairs, as individuals left the colony only after their partner had returned. Parents did not match their partner’s investment by actively co-adjusting their foraging efforts on a trip-by-trip basis. Yet, pair members were similar in their temporal and energetic investments during chick rearing.ConclusionBalanced investment levels over a longer time frame suggest that a coordination of effort may not require permanent co-adjustment of the levels of care on a trip-to-trip basis, but may instead rather take place at an earlier stage in the reproductive attempt, or over integrated longer time intervals. Identifying the drivers and underlying processes of coordination will be one of the next necessary steps to fully understand parental cooperation in long-lived species.

Annual Mortality Limit for Four Gull Species in the Atlantic Flyway

Abstract We estimated the allowable annual take of great black-backed gulls Larus marinus, herring gulls L. argentatus, ring-billed gulls L. delawarensis, and laughing gulls Leucophaeus atricilla in the U.S. portion of the Atlantic Flyway to help meet human safety and resource management goals. Gulls can pose a serious threat to aviation, negatively impact other colonial-nesting migratory bird species, and conflict with other human activities. We estimated an annual take limit using a model that incorporated intrinsic population growth rate, minimum population size, and a recovery factor for each species. We estimated intrinsic population growth by combining allometric with life table approaches. We used the recovery factor to restrict the take level of the great black-backed gull beyond that of the other species because of poor data quality and concern about its population status. The herring gull was the only species with comprehensive demographic data. Population sizes used in estimating potential take limit varied greatly among the four species, but estimates of intrinsic population growth rate were similar (range 0.118 to 0.197). The annual potential take limits for the four gull species were 7,963 for herring gulls, 2,081 for great black-backed gulls, 15,039 for laughing gulls, and 14,826 for ring-billed gulls. Comparing average annual take from 2012–2019 to our modeled potential take limit, overharvest has not occurred for great black-backed and laughing gulls, occurred once every 8 y for ring-billed gulls, and occurred over half the time for herring gulls.

When speed matters: The importance of flight speed in an avian collision risk model

Renewable energy continues to grow globally, and the number of offshore wind farms is set to increase. Whilst wind energy developments provide energy security and reduced carbon budgets, they may impact bird populations through collision mortality, habitat modification and avoidance. To date, avian collision mortality has received the most attention and collision risk models have been developed to estimate the potential mortality caused by wind turbines. The utility of these models relies not only on their underlying assumptions but also on the data available to ensure the predictions are informative. Using a stochastic collision risk model (sCRM; based on the Band collision risk model) as an example, we explore the importance of bird flight speed and consider how the assumptions of the model influence the sensitivity to flight speed. Furthermore we explore the consequences of using site-specific GPS-derived flight speed rather than a standard generic value, with Lesser Black-backed Gulls Larus fuscus as an example, and consider how this generic value is currently used. We found that the model was most sensitive to the parameters of bird density, non-avoidance rate and percentage of birds at collision risk height, as well as bird flight speed. Using site-specific flight speed data derived from GPS tags rather than a standard value reduced the predicted number of collisions. We highlight that within the model, both the estimation of the probability of collision (PColl) and the flux of birds are sensitive to the bird flight speed; this sensitivity acts in opposite directions but the two do not necessarily balance out. Therefore, when the sCRM is used as generally done, there is little difference in collision estimates if airspeeds (bird flight speed relative to air through which it is moving) are used rather than groundspeeds (bird flight speed relative to ground). Estimates of seabird collision rates in relation to offshore wind farms are impacting future offshore wind development. By using site specific flight speed estimates and, accounting for different speeds in relation to wind direction, we demonstrate that cumulative collision estimates can be affected, highlighting the need for more representative flight speed data and where possible site-specific data.

Faecal microbiota and antibiotic resistance genes in migratory waterbirds with contrasting habitat use

Migratory birds may have a vital role in the spread of antimicrobial resistance across habitats and regions, but empirical data remain scarce. We investigated differences in the gut microbiome composition and the abundance of antibiotic resistance genes (ARGs) in faeces from four migratory waterbirds wintering in South-West Spain that differ in their habitat use. The white stork Ciconia ciconia and lesser black-backed gull Larus fuscus are omnivorous and opportunistic birds that use highly anthropogenic habitats such as landfills and urban areas. The greylag goose Anser anser and common crane Grus grus are herbivores and use more natural habitats. Fresh faeces from 15 individuals of each species were analysed to assess the composition of bacterial communities using 16S rRNA amplicon-targeted sequencing, and to quantify the abundance of the Class I integron integrase gene (intI1) as well as genes encoding resistance to sulfonamides (sul1), beta-lactams (blaTEM, blaKPC and blaNDM), tetracyclines (tetW), fluoroquinolones (qnrS), and colistin (mcr-1) using qPCR. Bacterial communities in gull faeces were the richest and most diverse. Beta diversity analysis showed segregation in faecal communities between bird species, but those from storks and gulls were the most similar, these being the species that regularly feed in landfills. Potential bacterial pathogens identified in faeces differed significantly between bird species, with higher relative abundance in gulls. Faeces from birds that feed in landfills (stork and gull) contained a significantly higher abundance of ARGs (sul1, blaTEM, and tetW). Genes conferring resistance to last resort antibiotics such as carbapenems (blaKPC) and colistin (mcr-1) were only observed in faeces from gulls. These results show that these bird species are reservoirs of antimicrobial resistant bacteria and suggest that waterbirds may disseminate antibiotic resistance across environments (e.g., from landfills to ricefields or water supplies), and thus constitute a risk for their further spread to wildlife and humans.

Counting breeding gulls with unmanned aerial vehicles: camera quality and flying height affects precision of a semi-automatic counting method

The use of Unmanned Aerial Vehicles (UAVs) to monitor large colonies of seabirds avoids challenges associated with conventional methods, but manual image processing is expensive. Development of semi-automated analytical methods rely on high image spatial resolution, which requires a trade-off between securing low area coverage and high spatial resolution flying at low altitude vs high area coverage but low spatial resolution flying at higher altitudes. Increasing individual bird detection probabilities requires maximizing contrast between target and background, which can be enhanced using thermal sensors. We applied a semi-automatic analytical method to multispectral UAV derived imagery to count a mixed breeding colony of Herring Gulls (Larus argentatus) and Lesser Blackbacked Gulls (L. fuscus). We trained the computer to detect different image classes by their spectral signature in several orthomosaics obtained from UAV flights at different altitudes using different cameras. Highest agreement with the manual counts was achieved by low flying (20 m) using the highest camera resolution (97.7 ± 1.1% for the Herring Gulls, omission error 2.6%, commission error 0.5%; 94.8 ± 1.8% for Lesser Black-backed Gulls, omission error 6.5%, commission error 1.6%). Method precision varied between trials, confirming the importance of low altitude flying with high quality cameras, and a 40% reduction in detection noise from adding a thermal sensor.

Spatial variation and biovectoring of metals in gull faeces

We assessed the spatial variation in concentrations of ten metals in faeces of the lesser black-backed gull (LBBG) Larus fuscus wintering at seven localities in South-West Spain. We found high concentrations of metals in gull faeces, with several elements (As, Cu, Mo, Pb, Zn) locally exceeding (by 2 to 11 times) derived Lowest Effect Level (LEL) values. We also found strong spatial variation, related to the main pollution sources associated with the different sites. Faeces from Chipiona Port (Gulf of Cádiz) showed the highest levels of As; Cetina saltpans (Bay of Cádiz) ranked first for Pb, Zn and Mo, which was consistent with historic mining and industrial pollution; Doñana ricefields showed the highest levels of Mn, a highly available element in flooded areas; while landfills ranked first for Cd, Co, Cr, Cu and Ni, potentially associated with electronic waste. Furthermore, we demonstrate how faecal analysis can be used to quantify biovectoring of metals into specific localities, using LBBG movement ecology and census data. At Fuente de Piedra, a shallow, closed-basin lake important for waterbirds, we show that metal inputs by LBBG have increased in recent years, and long-term deposition (e.g., of Pb) may impact aquatic communities and ecological processes in this Ramsar site.

Long‐distance migrants vary migratory behaviour as much as short‐distance migrants: An individual‐level comparison from a seabird species with diverse migration strategies

As environmental conditions fluctuate across years, seasonal migrants must determine where and when to move without comprehensive knowledge of conditions beyond their current location. Animals can address this challenge by following cues in their local environment to vary behaviour in response to current conditions, or by moving based on learned or inherited experience of past conditions resulting in fixed behaviour across years.It is often claimed that long‐distance migrants are more fixed in their migratory behaviour because as distance between breeding and wintering areas increases, reliability of cues to predict distant and future conditions decreases. While supported by some population‐level studies, the influence of migration distance on behavioural variation is seldom examined on an individual level.Lesser black‐backed gulls Larus fuscus are generalist seabirds that use a diversity of migration strategies. Using high‐resolution multi‐year GPS tracking data from 82 individuals from eight colonies in Western Europe, we quantified inter‐ and intra‐individual variation in non‐breeding distributions, winter site fidelity, migration routes and timing of migration, with the objectives of determining how much variation lesser black‐backed gulls have in their migratory behaviour and examining whether variation changes with migration distance.We found that intra‐individual variation was significantly lower than variation between individuals for non‐breeding distributions, winter site fidelity, migration routes and timing of migration, resulting in consistent individual strategies for all behaviours examined. Yet, intra‐individual variation ranged widely among individuals (e.g. winter site overlap: 0–0.91 out of 1; migration timing: 0–192 days), and importantly, individual differences in variation were not related to migration distance.The apparent preference for maintaining a consistent strategy, present in even the shortest distance migrants, suggests that familiarity may be more advantageous than exactly tracking current environmental conditions. Yet, variation in behaviour across years was observed in many individuals and could be substantial. This suggests that individuals, irrespective of migration distance, have the capacity to adjust to current conditions within the broad confines of their individual strategies, and occasionally, even change their strategy.

Microplastic abundance in gull nests in relation to urbanization

Human activity and urbanization are having profound effects on natural landscapes and ecosystems. The presence and persistence of human-made materials such as microplastics can have major impacts on the health of organisms in both marine and terrestrial environments. We quantified microplastics in herring gull (Larus argentatus) and great black-backed gull (Larus marinus) nests at three colonies in the northeast United States that varied in their degree of urbanization: Jamaica Bay (JB) in New York City, Youngs Island (YI) on Long Island, New York, and Tuckernuck Island (TN) in Massachusetts. Nests in urban colonies contained a higher proportion of microplastics than those in the more remote colony. Our results link urbanization with microplastic accumulation in coastal environments and suggest that assessing microplastics in seabird nests could provide a means of evaluating microplastics encountered by seabirds and other coastal marine animals.

Investigating avoidance and attraction responses in lesser black-backed gulls Larus fuscus to offshore wind farms

Movements through or use of offshore wind farms by seabirds while commuting or foraging may increase the potential for collision with turbine blades. Collision risk models provide a method for estimating potential impacts of wind farms on seabird populations, but are sensitive to input parameters, including avoidance rates (ARs). Refining understanding of avoidance through the use of high-resolution empirical movement data has the potential to inform assessments of the collision impacts of offshore wind farms on seabird populations. We assessed the movements of GPS-tagged lesser black-backed gulls Larus fuscus from a breeding colony in northwest England to estimate the species’ AR and avoidance/attraction index (AAI) to nearby offshore wind farms. To investigate both macro- (0-4 km) and meso-scale (0-200 m) responses to wind turbines, we used calculations of AR and AAI based on simulated vs. observed tracks. We found that birds exhibited an AR of -0.15 (95% CI: -0.44 to 0.06), indicating a degree of attraction within 4 km of the wind farms. However, AAI values varied with distance from wind farm boundaries, with a degree of avoidance displayed between 3 and 4 km, which weakened as distance bands approach wind farm boundaries. Meso-scale avoidance/attraction was assessed with regard to the nearest individual turbine, and flight height relative to the rotor height range (RHR) of the nearest turbine. We found attraction increased below the RHR at distances <70 m, while avoidance increased within the RHR at distances approaching the turbine. We explore how high-resolution tracking data can be used to improve our knowledge of L. fuscus avoidance/attraction behaviour to established wind farms, and so inform assessments of collision impacts.

A 6-year survey of plastic ingestion by aquatic birds in southern Portugal

Anthropogenic litter in the environment is pervasive globally. Of particular concern are plastics because of their ubiquity, longevity in the environment and lethal effects. Plastics affect organisms at most levels of biological organisation but, even in well studied animals like birds, we have limited insight into species-specific vulnerability or temporal trends of ingestion. We examined stomach contents of four aquatic bird species over more than 6 years in southern Portugal. Of the 462 individuals analysed, 22.7% had ingested anthropogenic litter, predominantly plastics, most of which were clear or white in colour. The white stork (Ciconia ciconia) exhibited the highest frequency of occurrence of anthropogenic litter (61.1%) and of plastics specifically (55.6%), whereas the yellow-legged gull (Larus michahellis) had the lowest (13.4% for both anthropogenic litter and plastics). Similar frequencies of occurrence were found for the northern gannet (Morus bassanus) (22 and 20.3%) and the lesser black-backed gull (Larus fuscus) (21.4 and 20.8%). The composition of the plastic ingested varied throughout the study period for each species, but with no clear temporal pattern. Our results revealed the ubiquity and frequency of occurrence of plastic ingestion as well as clear differences among species, providing a basis for long-term monitoring of litter ingestion.

High levels of fluoroalkyl substances and potential disruption of thyroid hormones in three gull species from South Western France

Per- and poly-fluoroalkyl substances (PFAS) raised increasing concerns over the past years due to their persistence and global distribution. Understanding their occurrence in the environment and their disruptive effect on the physiology of humans and wildlife remains a major challenge in ecotoxicological studies. Here, we investigate the occurrence of several carboxylic and sulfonic PFAS in 105 individuals of three seabird species (27 great black-backed gull Larus marinus; 44 lesser black-backed gull Larus fuscus graellsii; and 34 European herring gull Larus argentatus) from South western France. We further estimated the relationship between plasma concentrations of PFAS and i) the body condition of the birds and ii) plasma concentrations of thyroid hormone triiodothyronine (TT3). We found that great and lesser black-backed gulls from South Western France are exposed to PFAS levels comparable to highly contaminated species from other geographical areas, although major emission sources (i.e. related to industrial activities) are absent in the region. We additionally found that PFAS are negatively associated with the body condition of the birds in two of the studied species, and that these results are sex-dependent. Finally, we found positive associations between exposure to PFAS and TT3 in the great black-backed gull, suggesting a potential disrupting mechanism of PFAS exposure. Although only three years of data have been collected, we investigated PFAS trend over the study period, and found that great black-backed gulls document an increasing trend of plasma PFAS concentration from 2016 to 2018. Because PFAS might have detrimental effects on birds, French seabird populations should be monitored since an increase of PFAS exposure may impact on population viability both in the short- and long-term.

Understanding PFAAs exposure in a generalist seabird species breeding in the vicinity of a fluorochemical plant: Influence of maternal transfer and diet.

Perfluoroalkyl acids (PFAAs) are a focus of scientific and regulatory attention nowadays. However, PFAAs dynamics in the environment and the factors that determine wildlife exposure are still not well understood. In this study we examined PFAAs exposure in chicks of a generalist seabird species, the lesser black-backed gull (Larus fuscus), breeding 49km away of a PFAAs hotspot (a fluorochemical plant in Antwerp, Belgium). In order to study the pathways of PFAAs exposure, we measured how chicks' PFAAs burden varied with age, sex, and body condition. In addition, we related PFAA concentrations to chicks' diet using stable isotope signatures. For this purpose, we studied plasma PFAA concentrations in 1-week and 4-week-old gull chicks. Only 4 (PFOS, PFOA, PFDA and PFNA) out of the 13 target PFAA compounds were detected. Measured concentrations of PFOS and PFOA were generally high compared to other seabird species but were highly variable between individuals. Furthermore, our results suggest that maternal transfer plays a significant role in determining chicks' PFAAs burden, and that there are variable sources of exposure for PFOS and PFOA during post-hatching development. The association between PFOS and specific stable isotopes (i.e. δ15N and δ13C) suggests a higher exposure to PFOS in birds with a predominantly marine diet. We also found that males' condition was positively associated with PFOS plasmatic concentration, probably due to the indirect effect of being fed a high quality (marine) diet which appears PFOS rich. Yet, exact exposure source(s) for PFOA remain(s) unclear. Given that PFOS concentrations measured in some chicks surpassed the toxicity reference value calculated for top avian predators, continued monitoring of exposure and health of this gull population, and other wildlife populations inhabiting the area, is highly recommended.

Breeding habitat loss reveals limited foraging flexibility and increases foraging effort in a colonial breeding seabird

BackgroundHabitat loss can force animals to relocate to new areas, where they would need to adjust to an unfamiliar resource landscape and find new breeding sites. Relocation may be costly and could compromise reproduction.MethodsHere, we explored how the Lesser black-backed gull (Larus fuscus), a colonial breeding seabird species with a wide ecological niche, responds to the loss of its breeding habitat. We investigated how individuals adjusted their foraging behaviour after relocating to another colony due to breeding site destruction, and whether there were any reproductive consequences in the first years after relocation. To this end, we compared offspring growth between resident individuals and individuals that recently relocated to the same colony due to breeding habitat loss. Using GPS-tracking, we further investigated the foraging behaviour of resident individuals in both colonies, as well as that of relocated individuals, as enhanced foraging effort could represent a potential driver of reproductive costs.ResultsWe found negative consequences of relocation for offspring development, which were apparent when brood demand was experimentally increased. Recently relocated gulls travelled further distances for foraging than residents, as they often visited more distant foraging sites used by residents breeding in their natal colony as well as new areas outside the home range of the residents in the colony where they settled.ConclusionsOur results imply that relocated individuals did not yet optimally adapt to the new food landscape, which was unexpected, given the social information on foraging locations that may have been available from resident neighbours in their new breeding colony. Even though the short-term reproductive costs were comparatively low, we show that generalist species, such as the Lesser black-backed gull, may be more vulnerable to habitat loss than expected. Long term studies are needed to investigate how long individuals are affected by their relocation in order to better assess potential population effects of (breeding) habitat loss.

Foraging ecology drives mercury contamination in chick gulls from the English Channel

Although mercury (Hg) occurs naturally, human activity is currently the greatest source of release and the ocean receives Hg inputs by rivers and atmospheric deposition. Seabirds including chicks serve as valuable bioindicators of Hg contamination, reflecting local contamination around the colony. This study investigates the ecological drivers (trophic position and foraging habitat) influencing Hg concentrations in blood and feathers of chicks of three sympatric marine gull species. Chicks were sampled between 2015 and 2017 in the Seine Estuary, one of the most Hg contaminated rivers in Europe, and in the Normand-Breton Gulf (the Chausey Islands), 200 km west, as a reference site with limited contaminant inputs. The trophic status of the chicks was evaluated based on the relative abundance of stable isotopes (δ13C, δ15N and δ34S). There was a tight correlation between Hg concentrations, as well as the abundance of stable isotopes, in blood and feathers. Great black-backed gull had the highest blood Hg concentrations of the species (1.80 ± 0.92 μg⋅g-1 dry weight (dw)); the Lesser black-backed gull had intermediate concentrations (0.61 ± 0.18 μg⋅g-1 dw); and the European herring gull had the lowest (0.37 ± 0.26 μg⋅g-1 dw). Individuals with the highest trophic position showed consistently the highest Hg concentrations. The positive relationship between Hg concentrations and the feeding habitat (marine vs terrestrial) indicated that the main source of Hg for gulls in the English Channel is marine prey. This exposure led to relatively high Hg concentrations in Great black-backed gull, which may produce toxic effects to individuals with potential consequences for their populations.

Interspecies comparisons of brominated flame retardants in relation to foraging ecology and behaviour of gulls frequenting a UK landfill

This study quantifies and compares concentrations and profiles of legacy and alternative (alt-) brominated flame retardants (BFRs) in the eggs of three gull (Laridae) species of international/UK conservation concern – great black-backed gulls (Larus marinus; n = 7), European herring gulls (L. argentatus; n = 16) and lesser black-backed gulls (L. fuscus; n = 11) in relation to their foraging ecology and behaviour in order to investigate potential exposure pathways at a remote landfill in western Scotland, UK. Egg concentrations of sum (∑) polybrominated diphenyl ethers (∑8PBDEs) in all three species exceeded those for most reported avian species using landfill, except for those in North America. Despite relatively high detection frequencies of ∑hexabromocyclododecanes (∑3HBCDDs) (94–100%), concentrations of ∑8PBDEs exceeded ∑3HBCDDs and ∑5alt-BFRs, with ∑8PBDE levels similar in all three species. Egg carbon isotopic (δ13C) values highlighted a greater marine dietary input in great black-backed gulls that was consistent with their higher BDE-47 levels; otherwise, dietary tracers were minimally correlated with measured BFRs. ∑3HBCDD egg concentrations of herring gulls markedly exceeded those reported elsewhere in Europe. Decabromodiphenylethane (DBDPE) was the only alt-BFR detected (6–14% detection rate), in a single egg of each species. The great black-backed gull egg contained the highest concentration of DBDPE measured in biota to date globally and provides strong evidence for its emerging environmental presence as a BDE-209 replacement in UK wildlife. Correlations between δ13C (dietary source) and some measured BFRs in eggs suggest multiple routes of BFR exposure for gulls frequenting landfill through their diet, behaviour, preening, dermal exposure and likely inhalation. The frequent use of landfill by herring gulls and their increased egg BFR burdens suggest that this species may be an important bioindicator of BFR emissions from such sites.

Mercury Uptake Affects the Development of Larus fuscus Chicks.

Current emission and mobilization rates of mercury (Hg) in the environment pose extensive threats to both wildlife and human health. Assessing the exposure risk and effects of Hg contamination in model species such as seabirds is essential to understand Hg risks at the population and ecosystem levels. The lesser black-backed gull (Larus fuscus), a generalist seabird species, is an excellent model species because it forages in both marine and terrestrial habitats, which in turn differ in their Hg exposure risk. To identify possible deleterious effects of Hg exposure on developing L. fuscus chicks, a dietary experiment was carried out and chicks were provided a marine, terrestrial, or mixed diet. The effects of embryonic and dietary Hg exposure on chick body condition and physiological state were assessed at different developmental stages until fledging age (30 d). Overall physiological condition was lower in chicks fed a predominantly marine diet, which coincided with higher Hg loads in blood and primary feathers. However, no effect of dietary uptake of Hg was observed on body condition or in terms of genotoxic damage. Body condition and genotoxic damage correlated instead with Hg exposure during embryonic development, which seems to indicate that embryonic exposure to Hg may result in carry-over effects on later chick development. Environ Toxicol Chem 2020;39:2008-2017. © 2020 SETAC.

Seabird-fishery interactions and bycatch at multiple gears in the Atlantic Iberian coast

Seabirds are marine predators known to forage in association with fisheries, however detailed knowledge on seabird-fishery interactions remains scarce in several regions of the world. We quantified seabird-fishery interactions and bycatch in central Portuguese coastal waters (NE Atlantic) between 2016 and 2018 in four gears: purse-seines, longlines, gillnets, and fishing traps. We mapped gear-specific fishing effort and seabird bycatch events and characterized fishery catches. Specific objectives were to determine separately for seabird-fishery interactions and bycatch (i) the gear with the highest rates, (ii) the most abundant species, and (iii) to assess the main drivers (i.e. year, season, gear, and fishery catch) of seabird-fishery interactions. Purse-seines had the highest seabird-fishery interactions, and the most abundant species were Yellow-legged and Lesser black-backed gulls, Northern gannet, and Cory's shearwater. Total seabird-fishery interactions varied inter-annually but not seasonally, indicating high total seabird numbers at fishing boats year-round. In contrast, higher fishery interactions were found during spring for Yellow-legged gulls. Age classes of individuals varied according to species, and fishery catches had a positive effect on seabird-fishery interactions. Seabird bycatch occurred mostly in longlines and within the ‘Ilhas Berlengas’ Special Protection Area. Northern gannet and Cory's shearwater were the most bycaught species, and species ecological traits seemed important in determining gear-specific bycatch. Our results suggest a strong influence of purse-seine and artisanal fisheries on seabirds in the NE Atlantic coast, and future studies should investigate the effects of these fisheries on seabird populations in other regions of the world.