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The management of mixed municipal waste can have an impact on wildlife and ecosystems. Previous studies have investigated how opportunistic species like gulls can react very fast to new landfills; however, the impact of landfill closure on bird populations is less investigated. Yet, there is a need to understand how fast and to what extent, animal populations can be adapted to new scenarios where the waste will not be deposited in landfill sites anymore. The aim is to determine the influence of landfill closures on apparent survival of a resident Yellow‐legged Gull (Larus michahellis) population, used as a model species showing short‐distance foraging movements, and with a high dependence on local food subsidies. Complementarily, we built some basic population growth models in order to determine how potential changes in survival (before/after landfill closure) will impact on population growth rate. Using a data set of 4,437 Yellow‐legged Gull chicks ringed in four colonies over a period of 13 years, we obtained evidence supporting that the apparent survival was affected by landfill closure, especially if the landfill was located within a buffer of 10 km around the colony. Landfill closure affected the survival of first‐year gulls (with a mean decrease of ~ 0.5–0.36), but not of older birds. Consequently, we did not detect a remarkable effect of landfill closures on population growth rate, probably due to the lack of effect on adult survival rates except for one of the surveyed colonies, where we found an annual decline of 7%. [ABSTRACT FROM AUTHOR]

The Bay of Biscay is an important non-breeding area for some Palaearctic gull species and populations. The aim of this work is to describe the spatial and temporal distributions of non-breeding gulls in the Bay of Biscay, and to identify their major areas of origin. With that goal, we analysed 6773 live sightings of colour-ringed gulls within the southeastern part of the Bay of Biscay during the 20 years 2000–19, relating to 2552 individuals of 10 species. Their distribution along the coast was not homogeneous, with numbers peaking in most cases from November to February, though some species were observed to peak around midsummer. Their origins comprised a wide geographical area encompassing western and eastern Europe; overall, the species can be divided into four groups by origin: northwestern France with Britain and Ireland, central western Europe (with a centroid in the Benelux region), eastern Europe, and the western Mediterranean. [ABSTRACT FROM AUTHOR]

Important biological parameters, such as movement and survival, can differ substantially between sexes, driving the demographic patterns of a population. Sex-dependent spatial segregation at the foraging grounds can evolve as a mechanism to reduce competition for resources between sexes, among other causes. Investigating such segregation, especially in scenarios of decreasing food availability, can contribute to understanding how birds adapt to a fast-changing world. The aim of the present study was to determine whether year-round movements and survival varied between sexes within a resident Yellow-legged gull Larus michahellis population. To this end we used live encounter data on colour-ringed Yellow-legged Gulls in northern Spain in the period 2009–2017. We used Generalized Linear Models to analyse distance to the colony of origin and multi-state models to estimate both survival and year-round movements, which did not provide evidence supporting an effect of sex on movement and survival. In contrast, distances travelled from the natal colony varied between seasons and all gulls were more likely to move greater than 100 km from natal sites. Juveniles showed lower survival rates (0.55) than older birds (0.90). Future research with GPS data might help to reveal, if existing, the occurrence of local spatial segregation between sexes that otherwise remains undetected. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

The movements of Mediterranean Yellow-legged Gulls Larus michahellis michahellis to the Bay of Biscay were analysed using sighting data of colour-ringed birds. A total of 1,270 sightings corresponding to 567 individuals was compiled over a 14-year period. Gulls originated mainly from colonies in the east of Iberia (52.7%), southern France (28.2%) and the Balearic Islands (17.3%). The proportion of the year spent in the Bay of Biscay decreased with age: first-year birds occurred on the coast of the Bay of Biscay throughout the year while older individuals were seen only from July to December. Overall, 39.7% of the birds were resighted in more than one calendar year. The return rate of adults and sub-adults was similar. The results confirm the importance of the Bay of Biscay as a non-breeding area (mainly in autumn and winter) for Yellow-legged Gulls from the Mediterranean, and suggest that this population should be considered as partially migratory. [ABSTRACT FROM AUTHOR]