Temporal and age-related dietary variations in a large population of yellow-legged gulls Larus michahellis: implications for management and conservation

The role of seabird foraging strategies on the uptake of mercury: A case study using gulls and shearwaters from the Portuguese coast

Mercury (Hg) is a non-essential element that bioaccumulates and biomagnifies in food webs through site-specific biogeochemical processes. Seabirds are valuable bioindicators of Hg contamination, yet certain regions, like the Portuguese coast, remain underrepresented. This study measured Hg concentrations in the blood of yellow-legged gulls (Larus michahellis), Audouin's gulls (Ichthyaetus audouinii), and Cory's shearwaters (Calonectris borealis) breeding along the Portuguese coastline. The influence of foraging ecology on Hg contamination was investigated using stable isotopes (δ13C, δ15N, δ34S) along with GPS-loggers. Thus, 52 % of the adults were at low risk (0.95-4.8 μg g-1 dry weight, dw), while 37 % were at moderate risk of Hg toxicity (>4.8 μg g-1 dw). The highest trophic positions (indicated by δ15N values) were associated with higher Hg concentrations, particularly in gulls from Deserta Island. Yellow-legged gulls foraging in terrestrial habitats (inferred from lower δ13C and δ34S values and GPS data) generally exhibited lower Hg concentrations, although patterns varied between regions. Gulls from Deserta Island had elevated Hg concentrations, likely because they feed on discarded demersal fish. In contrast, those from Porto showed some of the lowest concentrations, likely because they fed on terrestrial food. However, other factors not evaluated here, like age, sex, or even phylogeny could have also influenced Hg uptake and bioaccumulation and should not be disregarded in future research. This study highlights the critical role of foraging strategies in Hg contamination and stresses the importance of estimate food web-specific baseline isotopic composition to better understand how these differences may impact Hg trophic transfer.

Reighardia sternae Infection and Associated Lesions in a Yellow-Legged Gull (Larus michahellis) in Italy

Reighardia sternae is a pentastomid parasitising the respiratory system of larids and skuas, the pathological significance of which is still poorly understood. In this study, pentastomes found in the interclavicular air sac of a deceased and necropsied yellow-legged gull (Larus michahellis) were identified by parasitological and molecular methods and associated gross and histopathological lesions were evaluated. After morphological evaluation and molecular characterisation, the species R. sternae was identified. This is the first report of R. sternae infecting L. michahellis in Italy. Gross pathology showed generalised aerosacculitis, parabronchial edema, and enlargement of the heart, liver, and spleen. The systemic lesions found at histopathological examination were indicative of chronic cardiocirculatory failure, which led to the death of the gull. Moreover, inflammation was present throughout the lungs and air sacs in the form of some granulomas and diffuse small nodular aggregates rich in lymphocytes. The remnants of a parasite were observed within a granulomatous lesion in the lung, suggesting a primary host response to the parasite. These latter findings may suggest that the migration of R. sternae was the cause of the pathological granulomatous pictures in the examined yellow-legged gull.

Review of Current Strategies to Address Micronutrient Deficiencies (MNDs) in Ghana: A Scoping Review

To achieve the Sustainable Development Goals by 2030, low-income countries like Ghana will require strategizing towards sustainable reduction in micronutrient deficiency (MND) diseases and MND-related morbidity and mortality. A scoping review was conducted to identify the policy framework around MND intervention, the actors implementing MND-related strategies and documented evidence on which strategies worked across implementation stakeholders. Forty-six peer-reviewed articles were selected (n = 46) including studies on nutrition-sensitive intervention studies (n = 15) and nutrition-specific intervention (n = 31). Eligibility criteria for inclusion of information from articles and publications were based on report findings on nutrition-related programmes and policies conducted and implemented in Ghana and should have been published between 2000 and 2024. Databases adopted for this scoping review include Google Scholar, PubMed, ScienceDirect, AGORA, Hinari and JSTOR. This scoping review obtained a comprehensive picture of the nutrition situation in Ghana by gathering nutrition surveillance data depicting the different strategies employed to combat MNDs in Ghana. The scoping review identified several MND intervention strategies; however, the sustainability of the strategies required effective implementation guidelines, policies and programmes that address dietary deficits specific to a particular population.

Assessing the impacts of trace element contamination on the physiology and health of seabirds breeding along the western and southern coasts of Portugal

Coastal seabirds serve as sentinels of ecosystem health due to their vulnerability to contamination from human activities. However, our understanding on how contaminant burdens affect the physiological and health condition of seabirds is still scarce, raising the uncertainty on the species' vulnerability vs tolerance to environmental contamination. Here, we quantified 15 Trace Elements (TE) in the blood of gull (yellow-legged gull Larus michahellis and Audouin's gull Ichthyaetus audouinii) and shearwater (Cory's shearwater Calonectris borealis) adults, breeding in five colonies along the Portuguese coastline. Additionally, stable isotopes of carbon (δ13C) and nitrogen (δ15N) were quantified to elucidate foraging habitat and trophic ecology of adults, to identify potential patterns of TE contamination among colonies. We used immuno-haematological parameters as response variables to assess the influence of TE concentrations, stable isotope values, and breeding colony on adults' physiological and health condition. Remarkably, we found blood mercury (Hg) and lead (Pb) concentrations to exceed reported toxicity thresholds in 25% and 13% of individuals, respectively, raising ecotoxicological concerns for these populations. The breeding colony was the primary factor explaining variation in five out of six models, underlining the influence of inherent species needs on immuno-haematological parameters. Model selection indicated a negative relationship between erythrocyte sedimentation rate and both Hg and selenium (Se) concentrations, but a positive relationship with δ13C. The number of immature erythrocyte counts was positively related to Hg and Se, particularly in yellow-legged gulls from one colony, highlighting the colony-site context's influence on haematological parameters. Further research is needed to determine whether essential TE concentrations, particularly copper (Cu) and Se, are falling outside the normal range for seabirds or meet species-specific requirements. Continuous monitoring of non-essential TE concentrations like aluminium (Al), Hg, and Pb, is crucial due to their potential hazardous concentrations, as observed in our study colonies.

Among-colony variation in plastic ingestion by Yellow-legged gulls (Larus michahellis) across the western Mediterranean basin

The Mediterranean region is both a hotspot for biodiversity and for the accumulation of plastic pollution. Many species are exposed to this pollution while feeding, including a wide diversity of seabirds. Our objective was to investigate spatial variation in the quantity and types of plastic ingested by Yellow-legged gulls using information obtained from regurgitated pellets collected in 11 colonies. Anthropogenic debris, and particularly plastic, was found in pellets from all colonies, but the amount varied considerably. This among-colony difference was stable over the two years of study. The presence of marine prey and the proportion of agricultural area around the colonies significantly influenced the number of ingested plastics. As landfills close and garbage management improves, the availability of anthropogenic waste should decline. Following the response of gulls to these changes will be particularly useful for monitoring plastic pollution and for understanding the response of opportunistic wildlife to environmental modifications.

Changes in plastic ingestion by yellow-legged gulls (Larus michahellis) over the breeding season

Gulls can be particularly vulnerable to ingesting plastics when using anthropogenic food sources, with potential consequences for survival and reproductive success. Although birds are known to switch foraging habitats over the breeding season to provide higher quality food for chick provisioning, it is unclear what this means regarding the ingestion of plastics. Here, we tested whether breeding gulls decrease the amount of plastic ingested during reproduction by collecting pellets from a series of monitored nests at a large yellow-legged gull (Larus michahellis) colony in southern France. We found at least one plastic item in 83.9 % of the analyzed pellets, with the most abundant plastic type being polyethylene-based sheet plastic. As predicted, we found a slight decrease in the number of plastic items in pellets at chick hatching. These results suggest that gulls, like other birds, may adjust foraging habits to provide more digestible, less risky, food to chicks.

Fatty acids composition in yellow-legged (Larus michahellis) and lesser black-backed (Larus fuscus) gulls from natural and urban habitats in relation to the ingestion of anthropogenic materials

Urban habitats offer spatially and temporally predictable anthropogenic food sources for opportunistic species, such as several species of gulls that are known to exploit urban areas and take advantage of accessible and diverse food sources, reducing foraging time and energy expenditure. However, human-derived food may have a poorer nutritional quality than the typical natural food resources and foraging in urban habitats may increase birds' susceptibility of ingesting anthropogenic debris materials, with unknown physiological consequences for urban dwellers. Here we compare the fatty acids (FA) composition of two opportunistic gull species (the yellow-legged gull, Larus michahellis, and the lesser black-backed gull, Larus fuscus) from areas with different levels of urbanization, to assess differences in birds' diet quality among foraging habitats, and we investigate the effects of ingesting anthropogenic materials, a toxicological stressor, on gulls' FA composition. Using GC-MS, 23 FAs were identified in the adipose tissue of both gull species. Significant differences in gulls' FA composition were detected among the three urbanization levels, mainly due to physiologically important highly unsaturated FAs that had lower percentages in gulls from the most urbanized habitats, consistent with a diet based on anthropogenic food resources. The deficiency in omega (ω)-3 FAs and the higher ω-6:ω-3 FAs ratio in gulls from the most urbanized location may indicate a diet-induced susceptibility to inflammation. No significant differences in overall FA composition were detected between gull species. While we were unable to detect any effect of ingested anthropogenic materials on gulls' FA composition, these data constitute a valuable contribution to the limited FA literature in gulls. We encourage studies to explore the long-term physiological effects of the lower nutritional quality diet for urban dwellers, and to detect the sub-lethal impacts of the ingestion of anthropogenic materials.

Ingestion of anthropogenic materials by yellow-legged gulls (Larus michahellis) in natural, urban, and landfill sites along Portugal in relation to diet composition

Pollution is a global concern, increasing rapidly throughout marine and terrestrial ecosystems, and affecting many species. Urbanization enhances waste production, leading to the opening of landfills that constitute a spatially and temporally predictable food source for opportunistic species. Several species of gulls are known to exploit and breed in urban areas, taking advantage of accessible and diverse food resources. The exploitation of anthropogenic food subsidies at sea (e.g. fishery discards), urban sites, and landfills leads to debris ingestion by gulls with potential negative effects. Here we characterize anthropogenic debris ingested by yellow-legged gulls (Larus michahellis) along Portugal, by analysing the content of pellets collected in (1) natural and urban breeding locations, and in (2) urban and landfill resting sites, to assess seasonal patterns in the ingestion of anthropogenic debris. We also relate diet with the presence of anthropogenic debris. Debris materials were found in 28.8% of pellets from breeding locations (natural and urban) and in 89.7% of pellets from resting sites (urban and landfill). Gulls from the most urbanized breeding location exhibited higher levels of ingested materials during the entire breeding cycle, however, gulls from a natural breeding site also ingested high levels of debris during the pre-breeding season. At resting sites, small seasonal differences were detected in the number and mass of debris items ingested, which were both higher during spring and summer. Gulls that typically fed on pelagic fish had significantly less sheet and fragment plastics in their pellets. The presence of certain debris categories in gull pellets was positively related to the presence of some prey items, suggesting that gulls may accidentally ingest debris while foraging at multiple habitats. The quantity of anthropogenic materials ingested by gulls from urban locations and landfills indicates a need for improved waste management.

Recent Efforts to Recover Armeria berlengensis, an Endemic Species from Berlengas Archipelago, Portugal

Berlengas archipelago is a UNESCO world heritage site and the only location where Armeria berlengensis is found. This species faces various threats, namely, human disturbance, the presence of Carpobrotus edulis, yellow-legged gull, common-rabbit, and black-rat populations. Thus, exclusion areas were installed, which blocked the access of most Gulls, aiming to promote the recovery of A. berlengensis. Additionally, rabbits and rats were removed from the island. After six years of surveys, there has been an increase in the number of individuals of A. berlengensis in the exclusion areas, and a clear shift in the size structure of the A. berlengensis population. Significant changes in the height and diameter of the individuals were also noted. These findings indicate that the population of A. berlengensis is changing and becoming a healthier population. Principal component analysis results show a straightforward dissimilarity between the areas with A. berlengensis and those without the species and allowed the clustering of two groups: the rupicolous species and the nitrophilous species. A. berlengensis produces few seeds (seed set 3.4%), which raises concern regarding the long-term survival of the species. Thus, further conservation efforts must be implemented, such as the control of invasive species, gulls, and ruderals, to allow for the recovery of A. berlengensis.

Assessment of environmental health based on a complementary approach using metal quantification, oxidative stress and trophic ecology of two gull species (Larus michahellis & Larus audouinii) breeding in sympatry

Metal pollution is currently a major issue in marine ecosystems, as organisms, and particularly seabirds, are exposed and accumulating increased levels from several anthropogenic sources. A set of 13 metals were quantified in two gull species breeding in sympatry, and in two distinct colonies separated by ca. 400 km. Oxidative stress was measured, and stable isotope analyses were used to link metal contamination and oxidative stress with the trophic ecology of each species/population. There was a clear segregation of metal contamination between the two species and to a much lesser extent between colonies. Overall, Audouin's gull was the most contaminated species for most metals, once this species relies mainly on fish and other marine resources. The Yellow-legged gull feeds regularly on terrestrial food sources besides fish, which may dilute contamination levels. Oxidative stress responses were related with birds' trophic ecology and foraging habitat, but apparently not with metal contamination.

Humans shape the year-round distribution and habitat use of an opportunistic scavenger

Research focused on evaluating how human food subsidies influence the foraging ecology of scavenger species is scarce but essential for elucidating their role in shaping behavioral patterns, population dynamics, and potential impacts on ecosystems. We evaluate the potential role of humans in shaping the year-round distribution and habitat use of individuals from a typical scavenger species, the yellow-legged gull (Larus michahellis), breeding at southwestern Spain. To do this, we combined long-term, nearly continuous GPS-tracking data with spatially explicit information on habitat types and distribution of human facilities, as proxied by satellite imagery of artificial night lights. Overall, individuals were mainly associated with freshwater habitats (mean proportion, 95% CI: 40.6%, 36.9%-44.4%) followed by the marine-related systems (40.3, 37.7%-42.8%), human-related habitats (13.5%, 13.2%-13.8%), and terrestrial systems (5.5%, 4.6%-6.5%). However, these relative contributions to the overall habitat usage largely changed throughout the annual cycle as a likely response to ecological/physiological constraints imposed by varying energy budgets and environmental constraints resulting from fluctuations in the availability of food resources. Moreover, the tight overlap between the year-round spatial distribution of gulls and that of human facilities suggested that the different resources individuals relied on were likely of anthropogenic origin. We therefore provide evidence supporting the high dependence of this species on human-related food resources throughout the annual cycle. Owing to the ability of individuals to disperse and reach transboundary areas of Spain, Portugal, or Morocco, international joint efforts aimed at restricting the availability of human food resources would be required to manage this overabundant species and the associated consequences for biodiversity conservation (e.g., competitive exclusion of co-occurring species) and human interests (e.g., airports or disease transmission).

Microbial Ecology of the Western Gull (Larus occidentalis)

Avian species host diverse communities of microorganisms which have important roles in the life of birds, including increased metabolism, protection from disease, and immune system development. Along with high human populations and a diversity of human uses of coastal zones, anthropogenic food sources are becoming increasingly available to some species, including gulls. Anthropogenic associations increase the likelihood of encountering foreign or pathogenic bacteria. Diseases in birds caused by bacteria are a substantial source of avian mortality; therefore, it is essential to characterize the microbiome of seabirds. Here, we determined both core and environmentally derived microbial communities of breeding western gulls (Larus occidentalis) from six colonies in California and Oregon. Using DNA extracted from bacterial swabs of the bill, cloaca, and feet of gulls, 16S rRNA gene sequencing was performed targeting the V4 region. We identified a total of 8542 operational taxonomic units (OTUs) from 75 gulls. Sixty-eight OTUs were identified in gulls from all six colonies with the greatest representation from phyla's of Firmicutes, Proteobacteria, Bacteroidetes, and Actinobacteria. Overall, microbial richness based on Chao's Abundance-based Coverage Estimator (ACE) index was similar for all colonies (mean = 2347 OTUs) with the smallest coastal colonies having the highest richness (mean = 2626 OTUs) and the largest colonies, located farther off-shore, having the lowest (mean = 2068 OTUs). This survey represents the most in-depth assessment to date of microbes associated with western gulls, and the first study to identify both species-specific and environmentally derived bacteria across multiple populations.

Recently-adopted foraging strategies constrain early chick development in a coastal breeding gull

Human-mediated food sources offer possibilities for novel foraging strategies by opportunistic species. Yet, relative costs and benefits of alternative foraging strategies vary with the abundance, accessibility, predictability and nutritional value of anthropogenic food sources. The extent to which such strategies may ultimately alter fitness, can have important consequences for long-term population dynamics. Here, we studied the relationships between parental diet and early development in free-ranging, cross-fostered chicks and in captive-held, hand-raised chicks of Lesser Black-backed Gulls (Larus fuscus) breeding along the Belgian coast. This traditionally marine and intertidal foraging species is now increasingly taking advantage of human activities by foraging on terrestrial food sources in agricultural and urban environments. In accordance with such behavior, the proportion of terrestrial food in the diet of free-ranging chicks ranged between 4% and 80%, and consistent stable isotope signatures between age classes indicated that this variation was mainly due to between-parent variation in feeding strategies. A stronger terrestrial food signature in free-ranging chicks corresponded with slower chick development. However, no consistent differences in chick development were found when contrasting terrestrial and marine diets were provided ad libitum to hand-raised chicks. Results of this study hence suggest that terrestrial diets may lower reproductive success due to limitations in food quantity, rather than quality. Recent foraging niche expansion toward terrestrial resources may thus constitute a suboptimal alternative strategy to marine foraging for breeding Lesser Black-backed Gulls during the chick-rearing period.

Plastic and Non-plastic Debris Ingestion in Three Gull Species Feeding in an Urban Landfill Environment

Plastic debris is recognized as a widespread, common and problematic environmental pollutant. An important consequence of this pollution is the ingestion of plastic debris by wildlife. Assessing the degree to which different species ingest plastics, and the potential effects of these plastics on their health are important research needs for understanding the impacts of plastic pollution. We examined debris (plastic and other types) ingestion in three sympatric overwintering gull species (Herring gulls Larus smithsonianus, Great Black-backed Gulls Larus marinus, and Iceland Gulls Larus glaucoides) to understand how debris ingestion differs among species, age classes and sexes in gulls. We also assessed how plastic burdens were associated with body condition to investigate how gulls may be affected by debris ingestion. There were no differences among the species, age classes or sexes in the incidence of debris ingestion (plastic or otherwise), the mass or number of debris pieces ingested. We found no correlation between ingested plastics burdens and individual condition. Gulls ingested plastic debris, but also showed high levels of other debris types as well, including metal, glass and building materials, including a metal piece of debris found within an abscess in the stomach. Thus, when the health effects of debris ingestion on gulls, and other species that ingest debris, is of interest, either from a physical or chemical perspective, it may be necessary to consider all debris types and not just plastic burdens as is often currently done for seabirds.

Morphological and Molecular Assessment of Pentastomes from Gulls in Portugal

During 2016, 153 gulls, including 64 Larus fuscus and 89 Larus michahellis, were found crippled in south Portugal. They died in Wildlife Rehabilitation and Investigation Center-RIAS and were necropsied. Reighardia sternae infected 2 (3%, n = 64) L. fuscus and 4 (4%, n = 89) L. michahellis. Molecular analysis confirmed the morphological identification on the basis of total body length, maximum body width, length of anterior and posterior hooks, total length of oral apparatus, and other features of oral apparatus of R. sternae. Both sequenced individuals in this study displayed 100% sequence identity to R. sternae individuals obtained previously from Larus ridibundus in Spain and to Reighardia sp. from Larus belcheri in Peru. Reighardia sternae is reported here for the first time in L. michahellis and for the first time from Portugal.