Importance of predictable anthropogenic food subsidies for an opportunistic gull inhabiting urban ecosystems

Abstract

The provision of predictable anthropogenic food subsidies (PAFS) to urban wildlife has been recognized as an important trophic input in urban ecosystems. However, there is a lack of agreement about the benefits and harms of urban PAFS for avian species. While there are many studies about the impact of PAFS on birds, little information is available about the potential importance of PAFS on the ecology of urban gulls. In the present study, we aimed to evaluate the importance of human PAFS for the urban population of the yellow-legged gull (Larus michahellis) in the city of Barcelona, northeastern Spain. This opportunistic seabird is considered a pest species in urban areas. Specifically, by conducting a visual census in a location where PAFS were provided every week year-round, we examined the total number and age structure of gulls using this PAFS station. We identified the presence of yellow-legged gulls with some physical anomalies using the PAFS station. The results of this study suggest that PAFS may be an important artificial resource for urban yellow-legged gulls inhabiting Barcelona, used by either breeders or non-breeders, and also used by handicapped individuals. Based on these results, we suggest the regulation of this activity as a complement to other measures focused on the reduction of available food resources present in urban areas to manage this problematic species.