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.