Gull Populations Research Articles

Stress in the egg makes gull chicks fitter

Biologists have known for years that conditions experienced during early development can dramatically influence health and longevity through to adulthood. When the environment becomes persistently challenging or too unpredictable, mothers pass on the stress hormones produced in response to difficult conditions to their offspring developing in the womb or egg. It is commonly believed that these increases in stress exposure have detrimental consequences for developing creatures long into their futures, such as the increased risk of illness and reduced survival. However, the stress communicated to a developing embryo by its mother could also be an advanced warning, which helps the youngster to develop in ways that might improve its chances of survival later in life. In new research led by Jose Noguera and his team at the University of Vigo, Spain, they provide evidence suggesting that this might be the case.Noguera and colleagues headed out to Sálvora Island, off the Atlantic coast of northern Spain to study a wild breeding colony of yellow-legged gulls. The team stealthily monitored the birds as they laid their eggs and selected the first egg from 46 nests – the first laid egg is often the only one that hatches successfully – before injecting some with a stress hormone, corticosterone. Soon after the chicks hatched the researchers took a small blood sample to investigate how the hormone boost had affected the developing chicks by looking at the DNA packaged in the birds’ red blood cells. Knowing that the ends of each DNA chromosome are tipped with specialised structures, telomeres, which protect them from wearing down and generally shorten with age, the team decided to find out how the stress hormone in the chick's eggs affected the length of the telomeres. In addition, the team checked the enzyme, telomerase, which is responsible for building and maintaining telomeres, to find out how well prepared the youngsters were for the rigours of life after hatching.The researchers found that the chicks that were exposed to stress hormones as eggs had more active telomerase and longer telomeres compared to the chicks that had not received a corticosterone boost. These results suggest that increased exposure to stress during embryonic life leads to changes that might improve the chicks’ survival prospects. Interestingly, using data collected previously from the same population of gulls, they also showed that starting life after hatching with longer telomeres increases the chances of chicks surviving for at least up to 8 days. This time window corresponds to the period of highest mortality in this species as gull chicks face constant danger, competing with their siblings for food while predators lurk in the colony.Noguera's study suggests that maternally derived stress hormones may be a key mechanism through which mothers transmit valuable signals to their offspring that could help them to program their biology in preparation for life on the outside. More broadly, the team challenge the common view that increased levels of stress hormones in the egg inevitably incur costs for the developing chick as a consequence of poor maternal conditions. It seems, instead, that the mother's stressful gift to her offspring may provide an opportunity to make them fitter, at least during the earliest and most challenging stages of life.

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

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

Population status and trend of the threatened ivory gull Pagophila eburnea in Svalbard

The ivory gullPagophila eburneais a high-Arctic seabird associated with sea ice throughout the year. It breeds at high latitudes, mostly in the Atlantic sector of the Arctic. It is rare (<11500 breeding pairs globally) and remains one of the most poorly known seabirds in the world. Although Svalbard (Norway) supports breeding populations of international significance, the population trend in the region was unknown prior to this study. We conducted annual surveys of known breeding sites from 2006 to 2019 to estimate the size of the ivory gull population in Svalbard and to assess the population trend. We visited 117 colonies, 60 of which were new discoveries during this study. All breeding sites were situated in cliffs, and no ground-breeding ivory gulls were found. Based on the most complete survey in 2019, we estimated the Svalbard breeding population to be between 1500 and 2000 breeding pairs. We recorded an overall 40% decline in the number of breeding ivory gulls, but the trends varied significantly among colonies. The inter-annual fluctuations in the number of breeding pairs were not synchronous among colonies, which can be explained by the movements of adult breeding birds between colonies. The current decline in the Svalbard ivory gull population could be related to the ongoing decline in sea ice extent and quality in the Barents Sea. It may also be driven by ecological changes along the migration routes or at the wintering grounds, as hypothesized for the Canadian breeding population.

Influence of fisheries on the spatio-temporal feeding ecology of gulls along the western Iberian coast

Gulls are highly opportunistic seabirds, and the exploitation of fishery discards has led to many population increases worldwide. We investigated the importance of fish in the diet of yellow-legged Larus michahellis and Audouin’s gulls L. audouinii and assessed the influence of fishery discards on their feeding ecology. We collected pellets from 4 islands along the western Iberian coast during pre-breeding, breeding, and post-breeding seasons from 2014 to 2018. Stable isotopes (from adult blood, and chick and adult feathers) were used to investigate spatial, seasonal, and inter-annual differences in their feeding ecology. We used pellet, stable isotope (δ15N, δ13C, and δ34S), and biochemical (triglycerides, uric acid, total protein, and carotenoids in adult plasma) analyses to investigate their relationships with fish landings across the annual cycle. Results revealed that the fish species consumed by gulls matched those landed by local fisheries on all study islands, and there was a positive association of pelagic and demersal fish diets with fish landing quantities for 2 islands. δ34S values suggest different self-feeding and chick-provisioning strategies in relation to fisheries. δ15N values exhibited strong negative correlations with fish landings, and triglycerides were positively correlated with pelagic but not with demersal fish landing quantities, suggesting that gulls fed more on lower trophic level and higher energetic content pelagic fish than on demersal fish. Overall, our results based on several techniques suggest that gull feeding ecology was linked to fishery discards, which in view of the new EU landing obligation may have major implications for both gull populations across Europe.

The importance of marine resources in the diet of urban gulls

The availability of anthropogenic food subsidies has promoted an increase in generalist opportunistic gull species, which currently breed and forage on predictable anthropogenic resources (e.g. landfills). Here we investigated whether marine resources are still important to urban-dwelling gulls. We studied 4 natural and 2 urban yellow-legged gull Larus michahellis colonies and compared (1) diet composition (through pellet analysis) and (2) isotopic niches of adults and chicks, (3) diet delivered to chicks of different ages, and (4) fatty acid (FA) composition of fledglings, in order to assess diet composition, diversity and quality, and the relevance of marine prey for natural and urban gull populations. Adult urban gulls consumed considerably lower proportions of marine prey when compared to gulls from natural colonies; however, they fed their younger chicks (<20 d old) mostly with fish, representing 61-80% of their chick food deliveries. Refuse items were mostly delivered to chicks older than 20 d. Overall, urban isotopic niches were not completely distinct from those of natural colonies, in some cases sharing ca. 50% of their niche space. Fledglings from the most urbanized colony presented overall higher FA concentrations and diversity, but they were lacking some omega-3 FAs relevant to their physiology. Our results highlight the importance of marine resources in the diet of urban gulls, particularly during early chick rearing, the relevance of food sources in the area around the breeding colonies and the fact that urban gulls benefit from year-round reliable anthropogenic food resources.

Identifying important habitats for waterbird conservation at a Greek Regional Nature Park

BackgroundSmall coastal wetlands are vital sites for wintering waterbirds. Identifying important habitats is critical for managing waterbirds effectively. The Vourkari inlet is a small coastal wetland located near the capital Athens, within the most urbanized and industrialized area of Greece. We aimed at identifying the most important habitats for waterbirds at the Vourkari inlet during winter.MethodsData about habitat use and availability were collected for 14 waterbird species and for seven habitat classes. Habitat selection (Manly’s selection ratio), overlap indices (Pianka’s niche overlap index) and null models were calculated.ResultsAll the studied waterbird species selected available habitats nonrandomly. Shallow waters (0–2 m), were used by 13 waterbirds and selected by five waterbirds. Pools and channels were used and selected by 10 species. Mud was used by nine species and selected by six species. Mud with rocky substrate was used by nine species and selected by eight species. Medium (2–4 m) and deep (4–6 m) open water habitats were used by seven species and selected by four species. Halophytic vegetation was used by six species and selected by two species. Several habitats were selected by nationally important populations: mudflat habitats (i.e., mud, mud with rocky substrate and pools and channels) by Common Redshanks (Tringa totanus), halophytic vegetation by Little Egrets (Egretta garzetta), shallow waters by Common Shelducks (Tadorna tadorna) and medium and deep waters by Sandwich Terns (Thalasseus sandvicencis), whilst shallow waters and mudflat habitats were preferred by a possibly internationally important population of Mediterranean Gulls (Ichthyaetus melanocephalus). Although overlap in habitat use between species was generally low, null models indicated habitat sharing and a lack of competition.ConclusionsWaterbirds coexisted in the absence of competition for habitats at Vourkari, where they mostly used and preferred shallow water and mudflats. Small coastal wetlands are numerous, both in Greece and worldwide, therefore our findings would be useful as a basis for comparisons, both temporal at the inlet and spatial with other sites, that would help assess the importance of habitats and improve management strategies to benefit waterbirds, especially in areas with similar Mediterranean-type habitats and climate.

Seasonal ingestion of anthropogenic debris in an urban population of gulls

Gulls are generalist seabirds, increasingly drawn to urban environments where many species take advantage of abundant food sources, such as landfill sites. Despite this, data on items ingested at these locations, including human refuse, is limited. Here we investigate ingestion of prey and anthropogenic debris items in boluses (regurgitated pellets) from Pacific Gulls (Larus pacificus). A total of 374 boluses were collected between 2018 and 2020 in Tasmania. Debris was present in 92.51% of boluses (n = 346), with plastic (86.63%, n = 324) and glass (64.71%, n = 242) being the most prominent types. An abundance of intact, household items (e.g., dental floss, food wrappers) suggest the gulls regularly feed at landfill sites. In addition, the boluses are deposited at a roosting site located within an important wetland, thus we propose that the gulls may be functioning as a previously unrecognised vector of anthropogenic debris from urban centres to aquatic environments.

Effects of a new waste collection policy on the population of yellow-legged gulls, Larus michahellis, in the historic centre of Venice (Italy)

Urban sprawl represents one of the most critical threats to biodiversity leading to the decline of rare and specialist species and the proliferation of a few dominant generalist ones. Among the winners there is the yellow-legged gull, Larus michahellis, which has recently colonised towns, nesting on the roofs of buildings and feeding on urban waste by spreading the contents of garbage bags on the streets. This situation has been recently documented in the historic centre of Venice (Italy) where it led to negative environmental impact and serious consequences in terms of urban hygiene. To counter such problems, the public company responsible for managing the urban waste in the Venice municipality established a new waste collection policy in the city to prevent accumulation of rubbish in the streets and limit the amount of trophic resources available for the species. We performed a monitoring program of the urban population of yellow-legged gulls and used generalized linear models to investigate the effectiveness of the new waste collection system on reducing the amount of waste in the streets and its effect on the target species. Results revealed a statistically significant positive correlation between urban waste and gulls and a significant effect of the new policy in lowering these two variables. Open areas, strongly frequented, with food and beverage vendors and illegal dumps were also highlighted as the main contributors to the presence of yellow-legged gulls. Such information can be used by local authorities to plan specific interventions to reduce the attractiveness of the city to gulls.

Bidirectional transfer of halogenated flame retardants between the gastrointestinal tract and ingested plastics in urban-adapted ring-billed gulls

The hypothesis that plastics can transfer chemical pollutants to organisms after ingestion has been supported by several lab and field studies. However, models indicate that this transfer could be bidirectional and that whether chemicals move from plastics to the animal or vice versa, depends on several factors, including the relative concentrations of chemicals in both the animal and the plastics ingested. To explore this phenomenon in the field, we examined the relative concentrations of several halogenated flame retardants (HFRs) in a population of urban-dwelling ring-billed gulls (Larus delawarensis) and the plastics in their gastrointestinal (GI) tracts. We predicted the direction of transfer for HFRs between these birds and their ingested plastics using assumptions based on equilibrium theory. Because we were also interested in the sources of ingested plastics in this population, we investigated the relationships between time spent in different foraging habitats (determined using GPS-based telemetry) and the amounts and morphologies of plastics in their GI tracts. Results suggest that for this highly HFR-exposed population of ring-billed gulls, chemical transfer between plastics and bird is bidirectional, with a dominance of transfer from bird to ingested plastics. We also observed a relationship whereby birds that ingested no or low amounts of plastics were most closely associated with the use of residential habitats. Overall, we conclude that whether ingested plastics is a source or sink of chemicals to organisms is a complex and context-dependent phenomenon, and likely varies based on parameters such as exposure level and feeding ecology.

Adapting to urban ecosystems: unravelling the foraging ecology of an opportunistic predator living in cities

The increasing urbanisation of the natural environment affects species differently. While most species cannot cope with these human impacts, others can persist or may even be favoured in these anthropogenic ecosystems. Among the different urban-adapted wildlife species, the populations of different species of opportunistic gulls have increased in urban areas and some have established breeding populations at a global scale. Although the ecology of these predators is relatively well-known in their natural environment, accurate knowledge about their urban ecology is very scarce. Here, we investigated the foraging ecology (habitat use, spatial movements and feeding) of an urban population of yellow-legged gulls (Larus michahellis) inhabiting the city of Barcelona (north-eastern Spain). We examined the diet of this urban population by analysing the stomach contents of chicks distributed throughout the urban area of Barcelona. The foraging movements of breeding gulls were investigated using GPS devices and habitat landscape information. The results show that this urban population of yellow-legged gull exploits different food resources, highlighting the consumption of urban birds and marine resources from fishery discards. In line with the diet results, GPS tracking data indicated that although yellow-legged gulls were able to use different types of habitats close to the city, they mainly foraged in urban and fishing port areas. In conclusion, yellow-legged gulls have adapted to exploit the food resources associated with urban environments. This study provides useful information to discuss management options measures to control the yellow-legged gull populations nesting in urban areas.

Parental Birds Incubating Larger Clutches Regulate Their Field Metabolic Rates in Response to Environmental Changes

Species are capable of flexible energy allocation in response to changes in food availability. The extent to which individuals are able to adjust their energy allocation is presumed to be dependent on individual quality. Individuals of lower quality (i.e. better physiological condition) may be at an energy ceiling, and lack the reserves available to be able to expend more energy when environmental conditions deteriorate. Using the doubly labeled water method, we measured the field metabolic rates of free-ranging Black-tailed Gulls Larus crassirostris incubating two- and three-egg clutches during two consecutive years. Lower sea surface temperatures in 2013, compared with those in 2012, provided indirect evidence of poorer food availability in 2013 than in 2012. Parent gulls incubating three-egg clutches were able to increase their energy expenditure, in response to the poor food conditions in 2013, whereas those incubating two-egg clutches were not. Within a gull population we found heterogeneity of the energy allocation process in response to changes in food availability.

Evaluating the effect of distance to different food subsidies on the trophic ecology of an opportunistic seabird species

AbstractThe availability of food subsidies of anthropogenic origin has strong consequences on the trophic ecology and population dynamics of several opportunistic species. However, evidence suggests that the use of certain feeding sources is very local, and hence, potentially important food subsidies may have a relatively small area of influence, resulting in only limited impact from the large geographic‐scale perspective. In the south‐eastern part of the Bay of Biscay, the Yellow‐legged Gull Larus michahellis population is distributed across several colonies, which are located close to each other but have variable dependence on the landfills and fishing harbours in the area. This population is therefore a good model to test the influence of anthropogenic food subsidies on the trophic ecology of an opportunistic species at the local scale. Distance to the nearest fishing harbour showed a stronger effect on the diet of Yellow‐legged Gull chicks than distance to the nearest landfill site. Gulls notably reduced their consumption of marine prey (mostly comprised of fishing discards) in relation to decreasing distance of their colony to the nearest fishing harbour. This result has direct implications from a management standpoint, since fish discards were also found to have only a limited effect on diet at regional scales, but a very high impact at the local scale. Moreover, those colonies that consumed a higher proportion of marine prey showed better population trends. In line with European Union policies, a reduction in the availability of fish discards, together with the closure of landfill sites, will occur in the coming years, probably leading to a change in the trophic ecology and dynamics of Yellow‐legged Gull populations.

Evaluating UAV-based techniques to census an urban-nesting gull population on Canada’s Pacific coast

The use of unmanned aerial vehicles, or drones, in wildlife monitoring has increased in recent years, particularly in hard-to-access habitats. We used fixed-wing and quadcopter drones to census an urban-nesting population of Glaucous-winged Gulls in Victoria, Canada. We conducted our study over 2 years and asked whether (i) drones represent a suitable survey method for rooftop-nesting gulls in our study region; and (ii) Victoria’s urban gull population had increased since the last survey >30 years earlier. Using orthomosaic imagery derived from drone overflights, we estimated at least a threefold increase over the 1986 count reported for the entire city (from 114 to 346 pairs), and an approximate tenfold increase in the number of gulls nesting in the downtown core. Drones proved to be an excellent platform from which to census rooftop-nesting birds: occupied nests were readily discernible in our digital imagery, and incubating birds were undisturbed by drones. This lack of disturbance may be due to Victoria’s location in an aerodrome; gulls experience dozens of floatplane and helicopter flights per day and are likely habituated to air traffic. Glaucous-winged Gulls have declined considerably at their natural island colonies in the region since the 1980s. Our results indicate that although urban roofs provide replacement nesting habitat for this species, local gull populations have not simply relocated en masse from islands to rooftops in the region.

Testosterone and Triiodothyronine in Franklin's Gull (Leucophaeus pipixcan) Eggs

maternally derived hormones are known to influence the growth and development of offspring. the differential deposition of these maternally derived hormones into egg yolk is one way by which females can alter their chicks' growth or survival. yolk constituents, especially testosterone, have been described for a wide variety of species. however, few studies have focused on multiple maternally derived hormones regulated by independent axes in the endocrine system, and those studies that have, mainly focus on corticosterone and testosterone. in this study, within and among female variation in testosterone and triiodothyronine concentrations in egg yolks were measured in three free-living franklin's gull (leucophaeus pipixcan) populations. testosterone (t), but not triiodothyronine (t3), concentrations increase within a female's clutch such that eggs laid later in the clutch have increasingly higher concentrations (from a mean of 1.97 log pg t/mg yolk for the first egg to 2.98 log pg t/mg yolk for the third egg compared to a mean of 0.14 log pg t3/mg yolk for the first egg to 0.31 log pg t3/mg yolk for the third egg). both testosterone and triiodothyronine concentrations increase among females across the breeding season such that eggs laid later in the season have significantly higher hormone concentrations (mean of 2.37 log pg t/mg yolk and mean of -0.03 log pg t3/mg yolk) than eggs laid early in the season (mean of 1.95 log pg t/mg yolk and mean of -0.17 log pg t3/mg yolk).

Ecosystem change and population declines in gulls: Shifting baseline considerations for assessing ecological integrity of protected areas

In Lake Superior's Pukaskwa National Park (PNP) in northern Ontario, Canada, herring gull (Larus argentatus) population size is used as an indicator of ecological integrity. Since the 1970s, gull populations have declined by 70% suggesting deteriorating park conditions. However, most other rated park indicators show stable or positive trends. Here, we focus on reconciling these seemingly disparate trends through a better understanding of factors regulating PNP gull populations. Lake-wide declines in surface-schooling prey fish may be limiting aquatic food resources for PNP gulls. To investigate this, we examined gull population trends in different parts of the park in the context of food availability. Gull diets were assessed using regurgitated pellets, egg stable isotopes (nitrogen, carbon) and fatty acids. Population declines were more severe in southern PNP compared to northern PNP and inter-region differences in bird diets likely contributed to these population trends. Gulls in the south relied to a greater extent on dwindling aquatic food resources, i.e., prey fish, while birds in northern PNP supplemented their diets with anthropogenic foods, i.e., garbage. Recognizing that regional declines in aquatic food availability have occurred across eastern Lake Superior is important for the interpretation of PNP gull population trends. Wide-scale ecological changes affecting PNP suggest that factors limiting PNP's herring gull population are not park-specific but, instead, reflect broader ecosystem-wide changes. Defining an appropriate threshold based on current knowledge of ecological conditions on Lake Superior is critical for using herring gull populations as an indicator of park ecological integrity.

Habitat use of urban-nesting lesser black-backed gulls during the breeding season

Increasing urbanisation is detrimental for some animal species and potentially advantageous for others. Urban-nesting populations of gulls have undergone rapid population increases worldwide, which has resulted in an increase in human-gull conflicts. In order to inform management and conservation decisions in relation to these populations, more information is needed about the behaviour of these birds in urban settings and how they utilise their environment. This study combined Global Positioning System (GPS) tracking data of 12 urban-nesting lesser black-backed gulls, Larus fuscus, with habitat and behaviour data over three breeding seasons (2016–2018). Despite the proximity of marine areas (~10 km), the birds only made significant use of terrestrial environments, spending two-thirds of their time away from the nest in suburban and urban areas, and one-third in rural green areas. The gulls utilised suburban and urban areas more as their chicks grew and appeared to use diverse foraging strategies to suit different habitats. These results indicate that the range of potential foraging areas available needs to be considered in management decisions and that urban bird populations may not use the resources they are expected to.

Birds Behaving Badly: The Regulation of Seagulls and the Construction of Public Space

This article is about the socio‐legal construction of one of the least‐loved birds in the United Kingdom: the ‘seagull'. In particular, it is about how the gull has been brought within the realm of the ‘anti‐social', in a context in which urban‐nesting gulls (of which there are many in the United Kingdom) are cast as causing a great deal of public nuisance, ranging from noise, aggression, and mess, to attacks, injuries, and stress. The article examines the measures adopted by local authorities to regulate the gull population – and to regulate people, in the name of regulating gulls – and shows how a construction of the ‘seagull’ underpins and justifies this regulatory framework. It argues that the story of the regulation of seagulls in the United Kingdom is also a story about the construction of public space, to the point that the measures adopted here challenge the very idea of public space.

A Gull that Scarcely Ventures on the Ocean: Yellow-Legged Gulls Larus Michahellis Atlantis on the Oceanic Island of Madeira

The yellow-legged Gull Larus michahellis atlantis (YLG) is a generalist and opportunistic species that explores different habitats and resources and easily adapts to humanised environments, sometimes posing problems related to aircraft security, public health or predation on other species, for example. we examined the distribution and foraging behaviour of YLGs on the oceanic island of Madeira. GPS-GSM devices were deployed on ten breeding individuals and samples of blood (adults) and feathers (chicks) were collected to examine their stable isotope signatures in relation to those of their prey. Tracked YLGs did not migrate. Birds remained mostly inland during the day (up to 60% of fixes) and barely 5% of the fixes were at sea. Eighty-eight out of 192 gull trips to the sea were in interaction with local fishing vessels, 91% of which involving purse seiners that were active at night. The diet of the adult YLGs consisted of refuse, fish and small petrels, whereas the chick diet included mainly fish. YLGs on this oceanic island are strongly dependent on anthropogenic resources, scarcely relying on natural marine prey. The desired control of this gull population could perhaps be achieved by the reduction of accessibility to organic waste.-Romero, J., Catry, P., Menezes, D., Coelho, N., Silva, J.P. & Granadeiro, J.P. (2019). A gull that scarcely ventures on the ocean: yellow-legged Gulls Larus michahellis atlantis on the oceanic island of Madeira. Ardeola, 66: 101–112.

Exclusion of Ring-billed Gulls (Larus delawarensis) from recreational beaches using canid harassment

Abstract Ring-billed Gull (Larus delawarensis) populations have dramatically increased throughout their geographic range with the largest concentrations in the Great Lakes region of Canada and the United States. Large populations of gulls cause conflict with humans at recreational beaches, where their effects on human health and safety include bacteria contamination from gull feces. We used border collies to harass and exclude gulls from beaches in summer 2012 and 2013, then measured gull numbers and Escherichia coli. Dogs were effective at reducing gull numbers by 56–76% during continuous and noncontinuous dog treatment periods. Levels of E. coli were lower on dog-treated beaches, but only during the first half of the summer. Mixed modeling analysis showed presence of dogs was a strong predictor of gull numbers and E. coli levels, with variation among dogs, possibly related to age. Noncontinuous use of dogs, applied within an integrated beach management framework, can provide a nonlethal method for reducing gull use and E. coli levels at recreational beaches.

Exposure of yellow-legged gulls to Toxoplasma gondii along the Western Mediterranean coasts: Tales from a sentinel.

Efficiently tracking and anticipating the dynamics of infectious agents in wild populations requires the gathering of large numbers of samples, if possible at several locations and points in time, which can be a challenge for some species. Testing for the presence of specific maternal antibodies in egg yolks sampled on the colonies could represent an efficient way to quantify the exposure of breeding females to infectious agents, particularly when using an abundant and widespread species, such as the yellow-legged gull (Larus michahellis). We used such an approach to explore spatio-temporal patterns of exposure to Toxoplasma gondii, a pathogenic protozoan responsible of toxoplasmosis in humans and other warm-blooded vertebrates. First, we tested the validity of this approach by exploring the repeatability of the detection of specific antibodies at the egg level using two different immunoassays and at the clutch level using an occupancy model. Then, samples gathered in 15 colonies from France, Spain and Tunisia were analysed using an immunoassay detecting antibodies specifically directed against T. gondii. Prevalence of specific antibodies in eggs was overall high while varying significantly among colonies. These results revealed that T. gondii circulated at a large spatial scale in the western Mediterranean yellow-legged gull population, highlighting its potential role in the maintenance community of this parasite. Additionally, this study illustrates how species commensal to human populations like large gulls can be used as wildlife sentinels for the tracking of infectious agents at the human-wildlife interface, notably by sampling eggs.