Gull Larus Michahellis Research Articles

Evaluating the dependence of opportunistic Yellow‐legged Gulls (Larus michahellis) on marine habitat and fishing discards

Several bird species benefit from anthropogenic food subsidies, such as landfills and fishing discards, that are being reduced owing to introduced legislation. For instance, since 2019, Europe has passed legislation to reduce dramatically the amount of fisheries discards through the Landing Obligation (LO), which states that all fish species under Total Allowable Catch (TAC) should not be discarded at sea. This European discard ban is expected to impact some gulls, as several gull populations have been observed to be heavily reliant on this resource. In this work, GPS tracking data from adult Yellow‐legged Gulls Larus michahellis and Vessel Monitoring System (VMS) data (i.e. detailed data of the spatial distribution of fishing vessels) are used to determine the utilization of the marine habitat and the level of interaction of gulls with fishing activity offshore and discards in the south‐eastern part of the Bay of Biscay. We found that these gulls had a low use of the marine habitat (ca. 15%) compared with terrestrial habitats, in contrast to the ca. 40% of the diet of this population which comprises marine prey. Furthermore, we detected that most of the gull tracking positions at sea did not interact with the fishing vessels (an overlap of 21.5% between gulls and VMS data). Conversely, other gull populations of the Iberian Peninsula were found to depend much more strongly on fishing activity. Therefore, the Yellow‐legged Gull population of the SE Bay of Biscay did not obtain most of its fish prey from interactions with offshore fishing activity but most possibly by taking fish remains in harbours and by feeding themselves. Consequently, we expect a minimal effect of the European policies oriented to ban fishing discards offshore on this population, which would be more affected by policies directed towards the reduction of food availability in landfills or fish landing management in harbours.

Disturbance‐dependent Yellow‐legged Gull (Larus michahellis) predation on Larid chicks decreases with chick age

Predation is one of the key factors shaping the dynamics of animal populations. In birds, nest loss due to predation can be a significant cause of low reproductive success. Ground‐nesting birds are among the bird groups most susceptible to predation, mainly because their nests are easily accessible to a broad suite of potential predators. For these birds, anthropogenic disturbances can generate changes in nest predation risk by altering their antipredator behaviour and also by altering the behaviour of the predator species, i.e. the predator becoming much more aware of predation opportunities due to frequent disturbances and/or motivated to repeat predation attempts when some are successful. To date, most previous studies investigating this have focused on a single effect, either predation or disturbance, on chick survival. It remains unknown how the risk of predation with and without disturbance varies with chick age. In this study, we used behavioural observations to assess how the interaction between predators and disturbance affects predation risk in chicks and how this interacts with chick age. Specifically, we investigated the effect of disturbance caused by humans and stray dogs on the predation of Slender‐billed Gull Chroicocephalus genei chicks by Yellow‐legged Gulls Larus michahellis, and whether this depended on the age of the chicks. Our results revealed that disturbance had a significant positive effect on predation measures of Slender‐billed Gull chicks by Yellow‐legged Gulls, but that this effect was mediated both by disturbance type and the age of chicks. Stray dogs entering the colony had a stronger disturbance effect on chicks than passing humans, increasing predation risk by Yellow‐legged Gulls. Our results also showed that chick age interacts with disturbance type to determine the predation risk. This is probably mediated by chicks' capacity to escape predation by gathering in a single large crèche that runs into the water when disturbed. To preserve Slender‐billed Gull colonies in one of its few remaining breeding sites in Tunisia, and as gulls tend to react even when the disturbance occurs relatively far from the colonies, it is crucial to (1) restrict human access to dikes and islets where large colonies breed and (2) construct artificial islets attractive to gulls and inaccessible to stray dogs.

Sex determination based on morphometric measurements in yellow-legged gulls (Larus michahellis) around Istanbul

BackgroundYellow-legged gulls (Larus michahellis), commonly found in Istanbul and their surroundings, have a monomorphic plumage, like other gull species. For this reason, sex determination cannot be made externally. In this study, a total of 60 adult Yellow-legged gulls, 33 males, and 27 females, collected from the coastal areas of Istanbul, were examined. Discriminating functions were developed to classify males and females using birds that were previously sexed by DNA analysis and abdominal dissection.ResultsHead length and bill depth were selected to build the discriminant function by the stepwise analysis. The function classified male gulls with an accuracy of 97.0% and females with an accuracy of 92.6%. Head length alone is the most accurate predictor in terms of the percentage of correct sex determination (90.9% for males, 92.6% for females).ConclusionsFunctions that can easily determine sexual dimorphism for the population of Larus michahellis gulls around Istanbul have been put forward for the first time.

High philopatry rates of Yellow-legged Gulls in the southeastern part of the Bay of Biscay

BackgroundPhilopatry rate is one of the main factors shaping population dynamics in colonial seabirds. Low rates of philopatry are linked to populations with high dispersal, while high rates are linked to populations with a very high spatial structure pattern (i.e., metapopulations). The Cantabrian Yellow-legged Gull (Larus michahellis) population is considered to be resident, with relatively low dispersal rates. Precise estimations of its philopatry rates are however still lacking. Here, we aimed to estimate philopatry rates in the main Yellow-legged Gull colonies of the province of Gipuzkoa, in the southeastern part of the Bay of Biscay.MethodsWe analysed 734 resightings, during the breeding season at the colonies of Getaria, Santa Clara and Ulia, relative to a total of 3245 individuals ringed at birth in these same colonies during a period of 13 years. These data were analysed using Multi-State Recapture models in MARK.ResultsAfter controlling survival and resighting probability, the average dispersal rate among colonies was 4% (± SD = 2%) when individuals are immature, decreasing to 1 ± 1%) for adult breeding gulls (i.e., philopatry rate was 99%). Annual survival rates were assessed to be 0.27 ± 0.02 for birds in their first year of life and 0.87 ± 0.01 for older individuals. The probability of observing immature birds in the colonies was 0.08 ± 0.01, as compared to 0.21 ± 0.02 in adult birds.ConclusionsWe obtained evidence of extremely high local philopatry rates, clearly within the upper limit found in gulls. A high philopatry favour a speciation in these species who are vulnerable to obtain the main food source (landfills and fishing discard) which are transforming under new ecological process.

Molecular characterization of the re-emerging West Nile virus in avian species and equids in Israel, 2018, and pathological description of the disease

BackgroundIn this report we describe the molecular and pathological characteristics of West Nile virus (WNV) infection that occurred during the summer and fall of 2018 in avian species and equines. WNV is reported in Israel since the 1950s, with occasional outbreaks leading to significant morbidity and mortality in birds, high infection in horses and humans, and sporadic fatalities in humans.MethodsAnimal and avian carcasses in a suitable condition were examined by post-mortem analysis. Tissue samples were examined for WNV by RT-qPCR and the viral load was quantified. Samples with sufficient material quality were further analyzed by Endpoint PCR and sequencing, which was used for phylogenetic analysis. Tissue samples from positive animals were used for culturing the virus in Vero and C6/36 cells.ResultsWNV RNA was detected in one yellow-legged gull (Larus michahellis), two long-eared owls (Asio otus), two domesticated geese (Anser anser), one pheasant (Phasianus colchicus), four hooded crows (Corvus cornix), three horses and one donkey. Pathological and histopathological findings were characteristic of viral infection. Molecular analysis and viral load quantification showed varying degrees of infection, ranging between 70–1.4 × 106 target copies per sample. Phylogenetic analysis of a 906-bp genomic segment showed that all samples belonged to Lineage 1 clade 1a, with the following partition: five samples from 2018 and one sample detected in 2016 were of Cluster 2 Eastern European, two of Cluster 2 Mediterranean and four of Cluster 4. Four of the positive samples was successfully propagated in C6/36 and Vero cell lines for further work.ConclusionsWNV is constantly circulating in wild and domesticated birds and animals in Israel, necessitating constant surveillance in birds and equines. At least three WNV strains were circulating in the suspected birds and animals examined. Quantitative analysis showed that the viral load varies significantly between different organs and tissues of the infected animals.

Behavioral rhythms of an opportunistic predator living in anthropogenic landscapes

BackgroundHuman activities have profoundly altered the spatio-temporal availability of food resources. Yet, there is a clear lack of knowledge on how opportunistic species adapt to these new circumstances by scheduling their daily rhythms and adjust their foraging decisions to predicable patterns of anthropic food subsidies. Here, we used nearly continuous GPS tracking data to investigate the adaptability of daily foraging activity in an opportunistic predator, the yellow-legged gull (Larus michahellis), in response to human schedules.MethodsBy using waveform analysis, we compared timing and magnitude of peaks in daily activity of different GPS-tracked individuals in eleven different habitat types, in relation to type of day (i.e., weekday vs. weekend).ResultsDaily activity rhythms varied greatly depending on whether it was a weekday or weekend, thus suggesting that gulls’ activity peaks matched the routines of human activity in each habitat type. We observed for the first time two types of activity as modelled by waveforms analysis: marine habitats showed unimodal patterns with prolonged activity and terrestrial habitats showed bimodal patterns with two shorter and variable activity peaks.ConclusionsOur results suggest that gulls are able to fine-tune their daily activity rhythms to habitat-specific human schedules, since these likely provide feeding opportunities. Behavioral plasticity may thus be an important driver of expansive population dynamics. Information on predictable relationships between daily activity patterns of gulls and human activities is therefore relevant to their population management.

Breeding Yellow‐legged Gulls increase consumption of terrestrial prey after landfill closure

The ecology of opportunistic foragers can be highly dependent on anthropogenic food sources, such as landfills, resulting in changes in several ecological and demographic aspects. The total closure of several landfill sites and the use of deterrence systems to prevent access to the remaining open landfill sites in a region in the northern Iberian Peninsula provided an excellent opportunity to evaluate the consequences of landfills on the trophic ecology of an opportunistic forager, the Yellow‐legged Gull Larus michahellis, using these resources. Based on stable isotope analyses, we used mixing models to estimate changes in diet before and after the closure of the majority of landfills in the breeding and the non‐breeding season. We found a decrease in the consumption of food from landfills after their closure, which was accompanied by an increase in feeding on terrestrial prey (mostly earthworms), but only in the breeding season. Interestingly, we observed no increase in marine prey consumption after the landfill closures. In winter there was a decrease in terrestrial prey consumption, whereas the consumption of marine and, despite their reduce availability, landfill resources increased. Thus, and unlike when all the landfills were open, we detected significant trophic differences between breeding and non‐breeding seasons. Additionally, we found significant trophic differences among colonies that were quite close to each other, but not between breeding adults and chicks. In conclusion, landfill closure or the use of deterrence systems had a direct impact on the trophic ecology of Yellow‐legged Gulls; loss of refuse was mainly compensated for by prey of terrestrial origin when breeding, but not in winter. Thus, this species may experience foraging constraints in winter with potential effects on other life‐history aspects including their dispersal, breeding and survival that needs further evaluation.

The use of demersal trawling discards as a food source for two scavenging seabird species: a case study of an eastern Mediterranean oligotrophic marine ecosystem

BackgroundThe banning of fisheries discards by imposing an obligation to land unwanted catch constitutes a key point of the Common Fishery Policy reform proposed by the European Commission. The effect of such a ban on discards on top marine predators such as seabirds is largely unknown, especially in oligotrophic systems of the Mediterranean. The current study investigates the presence of scavenging seabirds around fishing trawlers as well as the exploitation of discards produced by bottom trawlers in the eastern Ionian Sea.MethodsOn-board observations were randomly conducted in May and December 2014, in order to record the presence and use of fishery discards by two common seabird species, namely, Scopoli’s Shearwater (Calonectris diomedea) and the Yellow-legged Gull (Larus michahellis).ResultsA total of 3400 seabirds were counted during May of which 2190 individuals were Scopoli’s Shearwaters and 1210 were Yellow-legged Gulls. The latter species was the only scavenger observed during winter and in total, 768 individuals were counted. Differences in species abundance in the study area are related to breeding phenology and migratory movements. The number of seabirds attending bottom trawler operations during morning and afternoon hours showed no significant differences for both seabird species. Both scavenging seabirds extensively exploited fishery discards, which were mainly demersal fish, and consumed 70–80% of the total fishery discards biomass; however, they appeared to avoid poisonous species and/or large-sized fish. Yellow-legged Gulls displayed kleptoparasitic behaviour on Scopoli’s Shearwater during feeding experiments. The number of such incidents depended on the number of gulls around the fishing vessel, with more than 90% success rates.ConclusionsConsidering the average annual biomass of discards estimations and the consumption rate found in this work, 106.1–117.9 t may be offered as a food subsidy to scavenging seabirds in the study area and should support a substantial part of local populations. Our results constitute baseline information on the annual amount of fishery discards and their exploitation rate by seabirds in the Ionian Sea, and suggest further work for a complete understanding of the potential impacts of the discards reform bill on seabirds.

Temporal and geographical variations of mercury and selenium in eggs of Larus michahellis and Larus audouinii from central Mediterranean islands

ABSTRACTIn this study, we determined mercury and selenium levels in abandoned unhatched eggs of the yellow-legged gull (Larus michahellis) and Audouin’s gull (Larus audouinii) collected during 2004–2005 from the Tuscan archipelago and Sardinia (Italy). The different feeding habits of the two species probably determine the different uptakes of trace elements, as the study shows highly significant differences for selenium and mercury levels as well as shell thickness and Hg:Se molar ratio values. Audouin’s gulls nesting on the coasts of the Tuscan archipelago showed significantly higher selenium levels than did gulls from colonies from the islands around Sardinia. Comparisons with a similar investigation previously conducted in the same area suggested that mercury and selenium concentrations, although in line with reports in the literature, were significantly lower than levels encountered in gulls in the early 1980s. Mercury (mg/kg d.w.) dropped from 8.631 to 5.030 in Audouin’s gulls and from 2.509 to 0.828 in yellow-legged gulls. The regional decline in mercury levels following reduced use of the metal in industry and the probable food depletion effects linked to the overfishing of fish prey of these two gull species are discussed as hypotheses that could explain the decrease in mercury levels found in eggs.

Predictable anthropogenic food subsidies, density‐dependence and socio‐economic factors influence breeding investment in a generalist seabird

Recent European policies on the ban of fishing discards and the closure of open‐air landfills are expected to reduce predictable and abundant food resources for generalist seabirds. In order to forecast the consequences of this reduction on seabird breeding investment it is important to understand whether diverse anthropogenic foraging resources act synergistically or not and whether their influence is mediated by density‐dependent mechanisms. To assess these effects at large spatio‐temporal scale, we measured mean egg volume as a proxy of breeding investment in ca 5000 three‐egg clutches of the yellow‐legged gull Larus michahellis from 20 colonies of the Western Mediterranean, located both along European and African coasts. In European gull colonies, egg volume increased with the availability of fishing discards and landfills in the vicinity of the colony. However, the landfill effect was weaker than the effect of fishing discards, probably due to the lower quality of waste as food for gulls. In contrast, none of the anthropogenic food subsidies influenced egg volume in African colonies, likely due to socio‐economic differences (i.e. a much lower availability and predictability of both discards and waste food. Finally, results showed that the positive association between fishing discards and open‐air landfills on egg volume was mediated by negative density‐dependent mechanisms probably related to an increase in competition for food.

Effects of decreased anthropogenic food availability on an opportunistic gull: evidence for a size‐mediated response in breeding females

Some opportunistic vertebrates exploit, and may largely rely upon, food generated by human activities. Better understanding the influence of this additional anthropogenic food on species' ecology would inform sustainable waste management. In the Balearic Archipelago of Spain, closure of an open‐air landfill site provided an experimental setting to measure the effect of removing anthropogenic food on the average body mass, breeding parameters and body condition of opportunistic Yellow‐legged Gulls Larus michahellis. After landfill closure there was a significant decline in the average body mass of breeding females and males (−10.4 and −7.8%, respectively), in average egg volume (−4.8%), and a shift in the modal clutch size from three to two eggs. Body condition decreased after landfill closure in both sexes. In breeding females, the drop in body weight was greater for birds with a low body size index. The differential response to a reduction of anthropogenic food between small and large birds suggests that food of anthropogenic origin contributes to tempering the effects of natural selection, making the long‐term demographic effects of changes in food supply difficult to predict.

Egg sampling as a possible alternative to blood sampling when monitoring the exposure of yellow-legged gulls (Larus michahellis) to avian influenza viruses

We explored whether antibody detection in egg yolks could serve as an alternative to antibody detection in plasma samples when monitoring yellow-legged gulls (Larus michahellis) for exposure to avian influenza viruses (AIVs). We tested female plasma and eggs for anti-AIV antibodies and used the data we obtained to check whether the two sample types yielded the same antibody status (positive or negative) and to compare the antibody prevalence estimated from the blood data with that estimated from the yolk data. Our results showed that sampling one egg per clutch, regardless of that egg's position in the laying sequence, is sufficient to provide an unbiased estimate of antibody prevalence across clutches. The results also showed that almost 25% of the clutches laid by positive females contained only antibody-negative eggs, which suggests that yolk samples might underestimate female antibody prevalence. However, this result may stem from differences in the methods used to assess plasma versus yolk antibody status. Further research is needed to clarify this issue; while the number of false negatives could be reduced by adapting antibody detection techniques, it may be that they are an unavoidable consequence of natural avian maternal transfer dynamics.

Comparing pellet and stable isotope analyses of nestling Bonelli's Eagle Aquila fasciata diet

Diet analyses are central to the study of avian trophic ecology, and stable isotope analyses have made an increasing contribution in the last two decades. Few isotopic studies have assessed the diet of raptor species, which are more frequently analysed by conventional diet methods such as pellet analysis. In this study, we compare prey consumption estimates of nestling Bonelli's Eagles Aquila fasciata from conventional pellet analysis (in terms of items and biomass) and stable isotopic mixing models (SIAR) using δ13C, δ15N and δ34S of feathers. The pellet analysis showed that European Rabbits Oryctolagus cuniculus, pigeons (mainly Common Wood Pigeons Columba palumbus and Domestic Pigeons Columba livia dom.), Red‐legged Partridges Alectoris rufa, passerines, Yellow‐legged Gulls Larus michahellis and Eurasian Red Squirrels Sciurus vulgaris were the main prey, so they were selected for diet reconstructions in SIAR. At the population level, mean prey consumption estimates were similar for pellets (both items and biomass) and SIAR. At the territory level, the weighted kappa statistic showed good ordinal scale agreement in main prey consumption between items or biomass and SIAR. Although the intraclass correlation coefficient showed poor method agreement when considering all prey in the same analysis, the intraclass correlation coefficients for each prey category showed significant agreement between pellets and SIAR when estimating the consumption of Rabbits, pigeons and Gulls, with lower agreement for passerines and Squirrels. Lastly, there was poor method agreement for estimates of Partridges. Our results suggest an overall agreement between the pellet analysis and SIAR when estimating nestling Bonelli's Eagle diet at both the population and, to a lesser extent, the territory level, supporting the usefulness of isotopic mixing models when identifying the terrestrial and marine components of raptor diets.

Living on predictability: modelling the density distribution of efficient foraging seabirds

In areas with regular fishing coastal fleets seabirds may benefit from the predictability of discards from fishing vessels, but it is not clear to what extent birds rely on this predictable resource and whether foraging is synchronized with the diel availability of discards. In this paper we investigate if a typical scavenger species, the yellow‐legged gull Larus michahellis, takes advantage of the temporal and spatial predictability of fish discards in the western Mediterranean Sea. The activity and distribution of the trawling fleet in this area is regulated and very predictable in time and space. We gathered aerial survey data across a relatively large area close to the coast to study the spatial distribution and density of L. michahellis, and modelled the density distribution of the species in relation to several oceanographic, ecological and temporal variables, using two different modelling approaches: MARS (multivariate adaptative regression splines) and GLM (generalized linear models). Our models suggest that the spatial density of trawlers at sea and the time of the day are the best explanatory variables of gull distribution, and that gulls concentrate in areas with vessels mainly during fish discarding time, supporting the hypothesis that gulls optimize time foraging to take advantage of fishery waste predictability. Additional surveys from the main gull roosting sites inshore support this hypothesis, as gulls start leaving to the sea just before fishing is completed and vessels begin discarding fish scraps when back to the harbour. This study represents one of the few examples of applying MARS to density distribution modelling, although its application to marine ecosystems should be conducted with caution because of large areas with real absence data. GLMs have shown to be more adaptable to such kind of data. Our data confirm the importance of fishery waste for L. michahellis, not only as a food resource but also as a major driver of their activity and distribution patterns. The ability of seabirds to predict accurately when a food resource will be available implies that modelling their distribution at sea needs to include such variables, both in spatial and temporal dimensions.

Hatching asynchrony and offspring sex: an experiment on maternal effects in the yellow-legged gull

Maternal effects may allow parents to increase their own fitness by adjusting progeny phenotype to pre- and post-natal conditions depending on the sex of individual offspring. In birds, sex-specific maternal effects can be mediated by predictable gradients of rearing conditions due to hatching asynchrony, egg laying date, order and mass, and brood sex ratio. In this study, we analysed the growth and survival consequences of experimentally reduced hatching asynchrony and order per se and in conjuction with other maternal effects (laying date, egg mass and sibling sex ratio) in yellow-legged gull (Larus michahellis) chicks of either sex. Survival of male chicks in synchronised broods was reduced compared to that of their sisters and that of male chicks in control broods, whereas survival of females but not that of males declined with hatching order independently of hatching synchronisation treatment. Survival of female but not male chicks declined with egg mass. In addition, survival of individual chicks, independently of their sex, was positively predicted by the proportion of females among their siblings. Hatching synchronisation resulted in larger average body size and in a weaker dependence of body mass on hatching order, suggesting that by modulating hatching asynchrony parents can effectively tune the size hierarchy among the offspring. Thus, survival of yellow-legged gull chicks of either sex was differentially affected by maternal effects as mediated by hatching asynchrony, hatching order as well as egg mass, which constitute predictable gradients of pre- or post-natal environmental conditions potentially under parental control.

Prevalence of Influenza A Antibodies in Yellow-Legged Gull (Larus michahellis) Eggs and Adults in Southern Tunisia

Investigating the prevalence of anti-influenza A viruses (AIV) antibodies in wild birds can provide important information for the understanding of bird exposure to AIV, as well as for prevention purposes. We investigated AIV exposure in nature by measuring the prevalence of anti-AIV antibodies in the nests and adults of an abundant and anthropophilic waterbird species common around the Mediterranean sea, the yellow-legged gull (Larus michahellis). Sampling took place in two colonies located in the gulf of Gabès in southern Tunisia: Sfax and Djerba. Antibodies were detected in the two sites, with higher prevalence in adults, eggs, and nests at Sfax than Djerba. Across both colonies, clutches that were laid later in the season, and, thus, more likely by younger parents, showed lower prevalence. Using patch occupancy modeling applied to egg clutches, we found that it is unnecessary to sample all the eggs in a given nest; nest status (antibody positive or negative) can be reliably estimated from a single egg. Differences in the density of birds, notably Larids, between the two sites may explain the observed differences in prevalence. The higher concentration of Larids in the Sfax colony could favor the transmission of AIV to yellow-legged gulls. This study highlights the importance of further developing ecological-based approaches to the factors determining the circulation of infectious agents in species such as the yellow-legged gull, which exist at the interface between diverse biological communities and human activities.

Contrasting patterns of wetland use by sympatric larids in winter

The population dynamics and behaviour of the larid assemblage of a Mediterranean coastal wetland, the Vourkari inlet in Greece, were studied during the winter of 2008–2009. More black-headed gulls (Larus ridibundus) were seen in the inlet in December, more Mediterranean gulls (Larus melanocephalus) were present from mid-January to mid-February, while little variation was observed in yellow-legged gull (Larus michahellis) numbers throughout winter. Bird numbers remained stable through the day for the yellow-legged gull, but fewer black-headed and Mediterranean gulls were present in the late morning than the other periods. Diurnal activity patterns showed that feeding was the primary behaviour for yellow-legged gulls and resting and sleeping for black-headed and Mediterranean gulls, with locomotion being equally important for all species. All larids were primarily feeding in the late morning period, but yellow-legged gulls were doing so in much higher proportions. These contrasting patterns suggested that the Vourkari inlet was more important as a day roost for black-headed and Mediterranean gulls and a preferred feeding ground for yellow-legged gulls. Furthermore, results suggested that resting and sleeping were interchangeable activities and all other activities had more or less the same time demands on a daily basis, and also a consistent pattern across species in sleeping proportions that might indicate cross-species synchrony in sleep patterns; however future research is needed to resolve these issues. This study provided important new information on the winter ecology of three larids and revealed patterns of wetland use by these species that could help assess the importance of certain areas and improve coastal habitat management strategies to benefit birds.

Insights into the spatiotemporal component of feeding ecology: an isotopic approach for conservation management sciences

AbstractAim Bringing new approaches to trace spatiotemporal variations in animals’ feeding ecology, which is fundamental for wildlife management and conservation since the accessibility of animals to trophic resources plays a key role in the dynamics of populations and metapopulations.Location Western Mediterranean coast.Methods The analysis of naturally occurring stable isotopes constitutes an exceptional approach to assess variations in the trophic ecology of species within the spatiotemporal dimensions. Here, we examined the spatiotemporal heterogeneity in resource exploitation of a nuisance and overpopulated gull species with a great feeding plasticity, the Yellow‐legged gull Larus michahellis, by measuring the stable isotope ratios of carbon (13C/12C, δ13C), nitrogen (15N/14N, δ15N) and sulphur (34S/33S, δ34S) in different wing feathers.Results Tracing isotopic changes among feathers in relation to moulting sequence, we showed that isotopic analyses on first primary feathers were good indicators of breeding trophic ecology, while others, such as eighth secondary feathers, reflected the feeding behaviour during the non‐breeding period. This knowledge was then used to report on estimations of seasonal feeding patterns throughout the year for seven gull populations along the Western Mediterranean coast.Main conclusions The high diversity in the exploitation patterns of the foraging habitats found in the study area both at spatial and at temporal scale indicated the opportunistic feeding behaviour of Yellow‐legged gulls. Proposed isotopic approach has revealed as a useful tool to evaluate spatiotemporal variations in the feeding ecology of populations which may become clue for dealing with the management of wild species, not only nuisance populations but also endangered species. We finally pointed out the relevance of the isotopic variability among individuals to infer diet diversity and food availability of a given population, thereby allowing demographic forecasts when trophic resources vary in abundance.

Culling Yellow‐legged Gulls Larus michahellis benefits Audouin's Gulls Larus audouinii at a small and remote colony

Capsule Culling of Yellow‐legged Gulls Larus michahellis can have some immediate local benefits to Audouin's Gulls in small and remote colonies. Aim To evaluate the effects of a Yellow‐legged Gull culling programme conducted from 2000 to 2009 on the breeding success and abundance of syntopic Audouin's Gulls on Alborán Island, Spain. Methods Censuses of nesting pairs and nest distribution maps for both gull species, and breeding success (well‐grown chicks per pair) monitoring for Audouin's Gulls, were conducted annually from April to July, 1994–2009, with complementary data for the period 1982–1994 available in an earlier study by the first author and colleagues. Results At the time of the peak occupation of the island Yellow‐legged Gulls seemingly reduced breeding success and number of nesting pairs of Audouin's Gulls. Negative effects on the colony of Yellow‐legged Gulls were observed when subjected to massive culling, which presumably favoured the breeding status of Audouin's Gulls. Conclusion The present study demonstrates that the facultative culling of large gulls affecting syntopic species of conservation concern can have some immediate local benefits in small and remote colonies. We suggest that culling Yellow‐legged Gulls in these zones could be justifiable, given the shortage of available breeding habitats for Audouin's Gulls.

Roof nesting by gulls for better or worse?

Since the early 1970s in Italy, the yellow‐legged gull Larus michahellis has been colonizing new kinds of nesting areas, in particular moorland and the rooftops of inhabited buildings. The incidence of rooftop colonies is now such that the yellow‐legged gull has come in many urban areas to be regarded as a pest. Yet its colony structure and breeding biology in the urban situation in Italy have remained largely undocumented. This paper reports observations of yellow‐legged gulls breeding in the town of Venice and in the surrounding lagoon during the 2003–2005 breeding seasons. The aim of this study was to examine the performance of birds breeding in natural and urban areas and to investigate the links between the natural and the newly established urban colony. For this, we analysed and compared factors indicative of breeder quality. Breeding performance was not substantially different in the two colonies. This suggests that gulls are successfully exploiting a new habitat, adapting to new resources, as other opportunistic species do.