Inter-species stimulus enhancement: herring gulls (Larus argentatus) mimic human food choice during foraging.

Herring gulls (Larus argentatus) are one of few species that thrive in anthropogenic landscapes, and their familiarity with people makes them an excellent target for studies of inter-species social cognition. Urban gulls pay attention to human behaviour in food-related contexts and, thus, we set out to investigate whether such cues can influence a gull's attention to and choice of potential food items in their environment. Herring gulls were given free choice of two differently coloured anthropogenic food items in the presence of a demonstrator, who was either sitting still or eating food from an item that matched one of the presented ones. We found that a demonstrator eating significantly increased the likelihood of a gull pecking one of the presented items. Furthermore, 95% of pecks were directed toward the presented food item that colour-matched the demonstrator's food item. The results showed gulls were able to use human cues for stimulus enhancement and foraging decisions. Given the relatively recent history of urbanization in herring gulls, this cross-species social information transfer could be a by-product of the cognitive flexibility inherent in kleptoparasitic species.

Environmentally relevant organophosphate triesters in herring gulls: In vitro biotransformation and kinetics and diester metabolite formation using a hepatic microsomal assay.

The in vitro biotransformation and kinetics of six organophosphate triester (OPE) flame retardants were investigated in herring gulls (Larus argentatus) from the Great Lakes using a hepatic microsomal metabolism assay. Administration of each individual OPE (tri-n-butyl phosphate (TNBP), tris(2-butoxyethyl) phosphate (TBOEP), triphenyl phosphate (TPHP), triethyl phosphate (TEP), tris(1,3-dichloro-2-propyl) phosphate (TDCIPP) and tris(2-chloroisopropyl) phosphate (TCIPP)) to the in vitro assay (concentration range 0.01 to 10µM) resulted in rapid depletion with the exception of TEP. Following the Michaelis-Menten enzyme kinetics model, a preliminary 2-minute incubation period was used to estimate the Vmax (±SE) values (i.e., the maximal rate of reaction for a saturated enzyme system), which ranged from 5.0±0.4 (TPHP) to 29±18pmol/min/mg protein (TBOEP), as well as the KM (±SE) values (i.e., the OPE concentration corresponding to one half of the Vmax), which ranged from 9.8±1 (TPHP) to 189±135nM (TBOEP). Biotransformation assays over a 100-minute incubation period revealed that TNBP was metabolized most rapidly (with a depletion rate of 73±4pmol/min/mg protein), followed by TBOEP (53±8pmol/min/mg), TCIPP (27±1pmol/min/mg), TPHP (22±2pmol/min/mg) and TDCIPP (8±1pmol/min/mg). In vitro biotransformation of OP triesters was clearly structure-dependent where non-halogenated alkyl OP triesters were metabolized more rapidly than halogenated alkyl triesters. Halogenated OP triesters were transformed to their respective diesters more efficiently relative to non-halogenated OP triesters. To our knowledge, this is the first study to investigate OP triester metabolism and OP diester formation in an avian or wildlife model system, which is important to understand the fate and biological activity of OPEs in an exposed organism.

Antimicrobial resistant bacteria in wild mammals and birds: a coincidence or cause for concern?

BACKGROUND: The emergence and dissemination of antimicrobial resistance (AMR) is a growing concern to public and animal health. The contribution attributable to wildlife remains unclear. In this study two unrelated wildlife species herring gulls (Larus argentatus) and a hybrid deer (Cervus elaphus x Cervus nippon) were investigated for the presence of Escherichia coli expressing an AMR phenotype. FINDINGS: Bacterial isolates resistant to ß-lactam compounds were identified in both animal species and the production of functional ß-lactamase was confirmed using nitrocefin. The prevalence of resistant isolates was higher in herring gulls (87%) compared to deer (31%). Resistance to this class of antibiotic was found only in non-pathogenic E. coli in herring gulls and in both pathogenic and non-pathogenic E. coli strains in deer. CONCLUSIONS: The presence of AMR in wildlife has implications for public health, food safety and potable water source protection among others.

Legacy contaminant trends in the Great Lakes uncovered by the wildlife environmental quality index.

Since the 1970s, wildlife managers have prioritized the recovery of Great Lakes ecosystems from contamination by Persistent Organic Pollutants (POPs). Monitoring and quantifying the region's recovery is challenged by the diversity of legacy contaminants in the environment and the lack of benchmarks for their potential biological effects. We address this gap by introducing the Wildlife Environmental Quality Index (WEQI) based on prior water and sediment quality indices. The tool summarizes, in a single score, the exposure of wildlife to harmful levels of multiple contaminants - with harmful levels set by published guidelines for protecting piscivorous wildlife from biological impacts. We applied the new index to a combined Canadian and American dataset of Herring Gull (Larus argentatus) egg data to elucidate trends in wildlife for eight legacy industrial pollutants and insecticides in the Great Lakes. Environmental quality of the Great Lakes region (as indexed by WEQI) improved by 18% between 2002 and 2017. Improvement came from reductions in both the scope of contamination (the number of guideline-exceeding contaminants) and its amplitude (the average size of guideline exceedances) at bird colonies. But recovery was unequal among lakes, with Lake Erie showing no improvement at one extreme. Weakly- or non-recovering lakes (Erie, Ontario, Huron) were marked by inconsistent improvement in scope and amplitude, likely due to ongoing loading, sediment resuspension and other stressors reported elsewhere. Fast-recovering lakes (Superior and Michigan), meanwhile, improved in both scope and amplitude. Contrasting trends and contaminant profiles (e.g., exceedances of PCBs versus DDTs) highlight the importance of lake-specific management for equalizing recoveries. Lower environmental quality at American than Canadian colonies, particularly in Lake Huron, further suggest uneven success in - and opportunities for - the binational management of wildlife exposure to legacy contaminants.

Plastic ingestion, accumulated heavy metals, and health metrics of four Larus gull species feeding at a coastal landfill in eastern Canada.

The objectives of this research were to assess ingested plastics and accumulated heavy metals in four urban gull species. Additionally, the relationships between ingested plastics and selected demographic and health metrics were assessed. Between 2020-2021 during the non-breeding seasons, 105 gulls (46 American herring gulls (HERG, Larus argentatus smithsonianus), 39 great black-backed gulls (GBBG, Larus marinus), 16 Iceland gulls (Larus glaucoides), 4 glaucous gulls (Larus hyperboreus)) were killed at a landfill in coastal Newfoundland and Labrador, Canada, as part of separate, permitted kill-to-scare operations related to aircraft safety. Birds were necropsied, the upper gastrointestinal tract contents were processed using standard techniques, and livers were analyzed for accumulated As, Cd, Hg, and Pb. The relationships between ingested plastics, demographics, and health metrics were assessed in HERG and GBBG. Across all four species, 85 % of birds had ingested at least one piece of anthropogenic debris, with 79 % ingesting at least one piece of plastic. We detected interspecific differences in plastic ingestion and hepatic trace metals, with increased ingested plastics detected in GBBG compared with HERG. For GBBG, levels of ingested plastic were relatively greater for birds with higher scaled mass index, while HERG with more ingested plastic had higher liver lead concentrations.

An ethogram identifies behavioural markers of attention to humans in European herring gulls (Larus argentatus).

Herring gulls (Larus argentatus) are one of few species thriving in anthropogenic landscapes. Their history of urbanisation and familiarity with people makes them a good target for studies of human-wildlife interactions. Previous research highlights a connection between food-stealing behaviour, success in anthropogenic areas, and increased attention towards humans, raising questions about the exact extent of a gull's knowledge of human food cues. To explore these, behavioural responses to human cues in a food-related context were investigated and presented in a systematic ethogram, which identified three distinct markers of attention. Head turns, approaches, and angular body position all differed significantly between control and food conditions, showing that attention towards humans in a food-related context was upregulated and reflected in behaviour. In food condition trials, head turns occurred more often and gulls faced more towards the experimenter with occasional approaches that were never seen in control conditions. Acoustic and behavioural human food-like cues alone seemed insufficient to elicit these responses, indicating that gulls specifically paid attention to the details of human behaviour or had specific knowledge of anthropogenic food items. These results show situation-dependent attentional modulation in gulls and provide a description of attentive behaviours that can be used in further study.

Nest sanitation behavior does not increase the likelihood of parasitic egg rejection in herring gulls.

Birds' behavioral response to brood parasitism can be influenced not only by evolution but also by context and individual experience. This could include nest sanitation, in which birds remove debris from their nests. Ultimately, nest sanitation behavior might be an evolutionary precursor to the rejection of parasitic eggs. Proximately, the context or experience of performing nest sanitation behavior might increase the detection or prime the removal of parasitic eggs, but evidence to date is limited. We tested incubation-stage nests of herring gulls Larus argentatus to ask whether nest sanitation increased parasitic egg rejection. In an initial set of 160 single-object experiments, small, red, blocky objects were usually rejected (18 of 20 nests), whereas life-sized, 3D-printed herring gull eggs were not rejected whether red (0 of 20) or the olive-tan base color of herring gull eggs (0 of 20). Next, we simultaneously presented a red, 3D-printed gull egg and a small, red block. These nests exhibited frequent nest sanitation (small, red block removed at 40 of 48 nests), but egg rejection remained uncommon (5 of those 40) and not significantly different from control nests (5 of 49) which received the parasitic egg but not the priming object. Thus, performance of nest sanitation did not shape individuals' responses to parasitism. Interestingly, parents were more likely to reject the parasitic egg when they were present as we approached the nest to add the experimental objects. Depending on the underlying mechanism, this could also be a case of experience creating variation in responses to parasitism.

Common Eider and Herring Gull as Contaminant Indicators of Different Ecological Niches of an Urban Fjord System.

Seabirds like gulls are common indicators in contaminant monitoring. The herring gull (Larus argentatus) is a generalist with a broad range of dietary sources, possibly introducing a weakness in its representativeness of aquatic contamination. To investigate the herring gull as an indicator of contamination in an urban-influenced fjord, the Norwegian Oslofjord, we compared concentrations of a range of lipophilic and protein-associated organohalogen contaminants (OHCs), Hg, and dietary markers in blood (n = 15), and eggs (n = 15) between the herring gull and the strict marine-feeding common eider (Somateria mollissima) in the breeding period of May 2017. Dietary markers showed that the herring gull was less representative of the marine food web than the common eider. We found higher concentrations of lipophilic OHCs (wet weight and lipid weight) and Hg (dry weight) in the blood of common eider (mean ± SE ∑PCB = 210 ± 126 ng/g ww, 60 600 ± 28 300 ng/g lw; mean Hg = 4.94 ± 0.438 ng/g dw) than of the herring gull (mean ± SE ∑PCB = 19.0 ± 15.6 ng/g ww, 1210 ± 1510 ng/g lw; mean Hg = 4.26 ± 0.438 ng/g dw). Eggs gave opposite results; higher wet weight and lipid weight OHC concentrations in the herring gull (mean ± SE ∑PCB = 257 ± 203 ng/g ww, 3240 ± 2610 ng/g lw) than the common eider (mean ± SE ∑PCB = 18.2 ± 20.8 ng/g ww, 101 ± 121 ng/g lw), resulting in higher OHC maternal transfer ratios in gulls than eiders. We suggest that the matrix differences are due to fasting during incubation in the common eider. We suggest that in urban areas, herring gull might not be representative as an indicator of marine contamination but rather urban contaminant exposure. The common eider is a better indicator of marine pollution in the Oslofjord. The results are influenced by the matrix choice, as breeding strategy affects lipid dynamics regarding the transfer of lipids and contaminants to eggs and remobilization of contaminants from lipids to blood during incubation, when blood is drawn from the mother. Our results illustrate the benefit of a multispecies approach for a thorough picture of contaminant status in urban marine ecosystems. Integr Environ Assess Manag 2021;17:422-433. © 2020 The Authors. Integrated Environmental Assessment and Management published by Wiley Periodicals LLC on behalf of Society of Environmental Toxicology & Chemistry (SETAC).

Inter-annual variation of mercury in aquatic bird eggs and fish from a large subarctic lake under a warming climate.

Understanding changes in environmental mercury concentrations is important for assessing the risk to human and wildlife populations from this potent toxicant. Here, we use herring gull (Larus argentatus) eggs to evaluate temporal changes in total mercury (THg) availability from two locations on Great Slave Lake (GSL), Northwest Territories, Canada. Egg THg concentrations increased through time, but this change was due to shifts in gull diets. Stable nitrogen isotopes allowed adjustment of egg THg concentrations for dietary changes. Diet-adjusted egg THg concentrations showed no long-term trend. Consistent with that result, new statistical analysis of THg concentrations in three species of GSL fish showed minor or no temporal changes. Although a long-term trend was absent, inter-year differences in adjusted egg THg concentrations persisted. Contributions of environmental variables (i.e., river flow, lake level, air temperature, precipitation, and wildfire) to these differences were investigated. Egg THg concentrations were greater following years of lower lake levels and greater wildfire extent. Lake level could have affected mercury methylation. Increased wildfire could have enhanced terrestrial Hg releases to the atmosphere where it was transported long distances to GSL. Climate change may increase wildfire extent with impacts on Hg bioaccumulation in northern ecosystems. Egg Hg levels reported here are unlikely to pose health risks to gulls, but in light of ongoing environmental change, monitoring should continue. Our study emphasizes the importance of ancillary datasets in elucidating Hg trends; such information will be critical for evaluating the effectiveness of Hg mitigation strategies implemented as part of the Minamata Convention.

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.

Molecular identification of four Sarcocystis species in the herring gull, Larus argentatus, from Lithuania.

BACKGROUND: Birds of the family Laridae have not been intensively examined for infections with Sarcocystis spp. To date, sarcocysts of two species, S. lari and S. wobeseri, have been identified in the muscles of gulls. The aim of the present study was to evaluate the species richness of Sarcocystis in the herring gull, Larus argentatus, from Lithuania. METHODS: In the period between 2013 and 2019, leg muscles of 35 herring gulls were examined for sarcocysts of Sarcocystis spp. Sarcocystis spp. were characterised morphologically based on a light microscopy study. Four sarcocysts isolated from the muscles of each infected bird were subjected to further molecular examination. Sarcocystis species were identified by means of ITS1 sequence analysis. RESULTS: Sarcocysts were detected in 9/35 herring gulls (25.7%). Using light microscopy, one morphological type of sarcocysts was observed. Sarcocysts were microscopic, thread-like, had a smooth and thin (about 1 µm) cyst wall and were filled with banana-shaped bradyzoites. On the basis of ITS1 sequences, four Sarcocystis species, S. columbae, S. halieti, S. lari and S. wobeseri, were identified. Furthermore, it was demonstrated that a single infected herring gull could host two Sarcocystis species indistinguishable under light microscopy. CONCLUSIONS: Larus argentatus is the first bird species found to act as intermediate host of four Sarcocystis spp. According to current knowledge, five species, S. falcatula, S. calchasi, S. wobeseri, S. columbae and S. halieti can use birds belonging to different orders as intermediate hosts.

Interindividual variation in the cytochrome P4501A response to 2,3,7,8-tetrachlorodibenzo-p-dioxin in herring gull embryo hepatocytes.

Exposure to dioxin-like compounds is consistently associated with concentration-dependent induction of cytochrome P4501A (CYP1A) enzymes in primary cultures of avian hepatocytes. We have previously demonstrated that the median effective concentration (EC50) for induction of this response is predictive of in vivo sensitivity to dioxin-like compounds in birds. We investigated sources of interindividual variation in the CYP1A response to 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) in wild herring gulls and considered how this variation may complicate dioxin sensitivity estimates based on the CYP1A bioassay. Concentration-dependent effects of TCDD on CYP1A mRNA expression were characterized in 55 hepatocyte cultures prepared from individual herring gull embryos. A large degree of variability was observed among the hepatocyte culture preparations. For example, 1) basal CYP1A4 and CYP1A5 mRNA expression varied by 20- and 126-fold, respectively, among individuals, and 2) exposure to TCDD induced CYP1A4 mRNA expression by 57-fold in the most responsive sample but did not significantly induce CYP1A4 mRNA expression above baseline values in 42% of hepatocyte culture preparations. Environmental and genetic factors contributing to the observed variability are discussed. Despite the large amount of interindividual variation, we conclude that reproducible EC50-based estimates of species sensitivity can be obtained from the CYP1A cell culture bioassay when samples are collected from relatively uncontaminated colonies. Environ Toxicol Chem 2019;38:660-670. © 2019 SETAC.

Seasonal changes in the preen wax composition of the Herring gull Larus argentatus.

The preen gland produces oily secretion, which smeared onto a bird's plumage improves its maintenance. The main components of the secretion are waxes, and its composition often changes during the year. The aim of this study was to determine the differences in the chemical composition of preen waxes in adult herring gulls Larus argentatus, captured in Poland in winter and in the breeding season. Preen gland secretions of herring gulls consist of monoester waxes, composed of about 29 saturated C7-C16 fatty acids and about 51 saturated C11-C20 alcohols. Unbranched-octanoic acid and n-hexadecanol dominated fatty acid and alcohol fractions, respectively, but 2-methyl-branched compounds were numerous in all individuals. The chemical compositions of fatty acids and alcohols differ between winter and the breeding season. In breeding gulls, 2-monomethyl-branched fatty acids were lower in content or could not be found, contrary to herring gulls in winter, where 2-monomethyl-substituted fatty acids were the second most abundant among all the fatty acids. Breeding gulls had also a higher content of n-octanoic acid and n-hexadecanol and a lower content of 2,6- and 2,8-dimethyl-substituted fatty acids than individuals caught during the winter. Differences in fatty acid composition were greater in breeding males, which incubate more often at night than breeding females. Hence, chemical changes in the preen wax composition in males may have evolved as additional nocturnal protection against mammalian predators which use olfaction to detect their prey and which are more active at night; however, this needs to be tested. Olfactory-based mate recognition in the colony also cannot be excluded at this stage of experimentation.

Inhalation - Route of EDC exposure in seabirds (Larus argentatus) from the Southern Baltic.

Despite the presence of endocrine disrupting mercury, PAHs, alkylphenols and bisphenol A in inhaled air, scientific literature lacks information on their penetration into the lungs. Large lung capacity in birds makes this route of penetration more significant than in other animals. The studies were conducted on lungs of herring gulls found in the Gulf of Gdansk area. The results were juxtaposed with other tissues, including the intestines, which reflect the main, alimentary penetration route of harmful substances into the organism. It was determined that the capacity of bird's lungs, affects the efficiency with which mercury is absorbed from the air. Birds found to have high mercury concentrations in lungs had low PAHs concentrations, what was determined by the fact that the birds foraged in two different areas, as well as on different trophic levels. The alimentary route of phenol derivatives into the organism was of greater significance than inhalation.

Miniaturization of a transthyretin binding assay using a fluorescent probe for high throughput screening of thyroid hormone disruption in environmental samples.

Thyroid hormone (TH) disrupting compounds are potentially important environmental contaminants due to their possible adverse neurological and developmental effects on both humans and wildlife. Currently, the most successful bio-analytical method to detect and evaluate TH disruptors, which target the plasma transport of TH in environmental samples, is the radio-ligand thyroxine-transthyretin (T4-TTR) binding assay. Yet, costly materials and tedious handling procedures prevent the use of this assay in high throughput analysis that is nowadays urgently demanded in environmental quality assessment. For the first time a miniaturized fluorescence T4-TTR binding assay was developed in a 96 well microplate and tested with eight TH disrupting compounds. For most of the compounds, the sensitivity of the newly developed assay was slightly lower than the radio-ligand binding assay, however, throughput was enhanced at least 100-fold, while using much cheaper materials. The TH disrupting potency of 22 herring gull (Larus argentatus) egg extracts, collected from two different locations (Musvær and Reiaren) in Norway, was evaluated to demonstrate the applicability of the assay for environmental samples.

Detection of Wellfleet Bay Virus Antibodies in Sea Birds of the Northeastern USA.

Wellfleet Bay virus (WFBV) is a recently described orthomyxovirus isolated from the tissues of Common Eiders (Somateria mollissima) collected during recurrent mortality events on Cape Cod, Massachusetts, US. Coastal Massachusetts is the only location where disease or mortality associated with this virus has been detected in wild birds, and a previous seroprevalence study found a significantly higher frequency of viral exposure in eiders from this location than from other areas sampled in North America. This suggests that coastal Massachusetts is an epicenter of WFBV exposure, but the reason for this is unknown. Opportunistic sampling of sympatric species and testing of banked serum was used to investigate potential host range and spatiotemporal patterns of WFBV exposure. Antibodies were detected in Herring Gulls (Larus argentatus), Ring-billed Gulls (Larus delawarensis), a White-winged Scoter (Melanitta fusca), and a Black Scoter (Melanitta nigra). These findings demonstrate the likely occurrence of fall/winter transmission, expand our understanding of the host range of the virus, and provide further insight into the epidemiology of WFBV in the northeastern US.

Developmental toxicity of PFOS and PFOA in great cormorant (Phalacrocorax carbo sinensis), herring gull (Larus argentatus) and chicken (Gallus gallus domesticus).

Perfluoroalkyl acids (PFAAs) are found globally in environmental samples and have been studied in various species. In this study, we compare the sensitivity of three avian species to the toxic effects of perfluorooctane sulfonate (PFOS) and perfluorooctanoate (PFOA). Eggs of great cormorant (Phalacrocorax carbo sinensis), herring gull (Larus argentatus) and the domestic White Leghorn chicken (Gallus gallus domesticus) were exposed in ovo by injection into the air sac. Effects on embryo survival were observed following exposure to PFOS and PFOA in chicken and herring gull. Chicken was found to be the most sensitive species with 50 % reduced embryo survival at 8.5 µg/g egg for PFOS and 2.5 µg/g egg for PFOA. Cormorant was shown to be the least sensitive species. The difference in sensitivity between chicken and herring gull was a factor of 2.7 for PFOS and 3.5 for PFOA. Between chicken and great cormorant, the sensitivity difference was 2.6 for PFOS and 8.2 for PFOA. Effects on embryo survival were seen at egg injection doses of PFOS close to levels found in environmental samples from wild birds, indicating that PFOS could be having effects in highly exposed populations of birds. This study also shows that there are differences in species sensitivity to PFOS and PFOA that should be taken into consideration in avian wildlife risk assessment.

GPS tracking data of Lesser Black-backed Gulls and Herring Gulls breeding at the southern North Sea coast.

In this data paper, Bird tracking - GPS tracking of Lesser Black-backed Gulls and Herring Gulls breeding at the southern North Sea coast is described, a species occurrence dataset published by the Research Institute for Nature and Forest (INBO). The dataset (version 5.5) contains close to 2.5 million occurrences, recorded by 101 GPS trackers mounted on 75 Lesser Black-backed Gulls and 26 Herring Gulls breeding at the Belgian and Dutch coast. The trackers were developed by the University of Amsterdam Bird Tracking System (UvA-BiTS, http://www.uva-bits.nl). These automatically record and transmit bird movements, which allows us and others to study their habitat use and migration behaviour in great detail. Our bird tracking network is operational since 2013. It is funded for LifeWatch by the Hercules Foundation and maintained in collaboration with UvA-BiTS and the Flanders Marine Institute (VLIZ). The recorded data are periodically released in bulk as open data (http://dataset.inbo.be/bird-tracking-gull-occurrences), and are also accessible through CartoDB and the Global Biodiversity Information Facility (GBIF).

Characterization of AhR agonists reveals antagonistic activity in European herring gull (Larus argentatus) eggs.

European herring gull (Larus argentatus) eggs from two Norwegian islands, Musvær in the south east and Reiaren in Northern Norway, were screened for dioxins, furans, and dioxin-like and selected non-dioxin-like polychlorinated biphenyls (PCBs), and subjected to non-target analysis to try to identify the aryl hydrocarbon receptor (AhR) agonists, responsible for elevated levels measured using the dioxin responsive chemically activated luciferase expression (DR-CALUX) assay. Eggs from Musvær contained chemically calculated toxic equivalent (WHO TEQ) levels of between 109 and 483 pg TEQ/g lw, and between 82 and 337 pg TEQ/g lw was determined in eggs from Reiaren. In particular PCB126 contributed highly to the total TEQ (69-82%). In 19 of the 23 samples the calculated WHO TEQ was higher than the TEQCALUX. Using CALUX specific relative effect potencies (REPs), the levels were lower at between 77 and 292 pg/g lw in eggs from Musvær and between 55 and 223 pg/g lw in eggs from Reiaren, which was higher than the TEQCALUX in 16 of the 23 samples. However, the means of the REP values and the TEQCALUX were not significantly different. This suggests the presence of compounds that can elicit antagonist effects, with a low binding affinity to the AhR. Non-target analysis identified the presence of hexachlorobenzene (HCB) (quantified at 9.6-185 pg/g lw) but neither this compound nor high concentrations of PCB126 and non-dioxin-like PCBs could explain the differences between the calculated TEQ or REP values and the TEQCALUX. Even though, for most AhR agonists, the sensitivity of herring gulls is not known, the reported levels can be considered to represent a risk for biological effects in the developing embryo, compared to LC50 values in chicken embryos. For human consumers of herring gull eggs, these eggs contain TEQ levels up to four times higher than the maximum tolerable weekly intake.

A transactional analysis of changes in parent and chick behaviour prior to separation of Herring Gulls (Larus Argentatus): A three-term contingency model.

The effect of the passage of time on parent-offspring behaviour of urban Herring Gulls (Larus Argentatus) was studied and analysed using a three-term contingency model. A behavioural sequence was initiated by the arrival of a parental adult gull, which would lead to feeding in the chick. However, with the passage of time, and approach of the separation period, this pattern changed. Chicks' begging became more intense, and parent gulls more often withheld food. However, the chicks' begging became directed at a wider range of adults over the observation period. These activities are placed within a three-term contingency model, which may have implications for understanding some behavioural processes involved in parent-offspring separation.