COVID-19 triggered a lockdown that paralyzed the entire planet for a few months. The effectsof this standstill were so remarkable in such a short time that it was proposed to call this periodthe Anthropopause. The Anthropopause produced an optimal scenario to study the effects ofbehavioural and ecological changes associated with human activities, as in the case of theyellow-legged gull (Larus michahellis), an opportunistic predator highly adapted to inhabit andexploit human-related environments. Several studies have demonstrated the close relationshipbetween the ecology of this and similar opportunistic gulls and anthropogenic food subsidesassociated to human activities. In this study, we assess the effects of the Anthropopause on thediet and habitat use of the urban population of yellow-legged gull breeding in the city ofBarcelona (northeastern Spain). For this, the diet of gull chicks sampled along the urbanecosystem before, during and after Anthropopause was examined by combining the analysis oftheir stomach contents (n=209) and the stable isotope values of δ13C, δ15N and δ34S of theirfeathers (n=119). We also GPS-tracked the movement of 64 gulls of different age classes(juveniles, immatures, and adults) to compare habitat use before and after the Anthropopause.The results showed a decrease in the consumption of urban birds and demersal species and anenrichment of δ13C values during the Anthropopause. Trophic niches inferred from stomachcontents and stable isotopes also decreased during the Anthropopause. In overall, the type ofhabitat used by GPS-tracked juvenile and adult gulls did not change one year after theAnthropopause compared to the use by the same age groups during previous years. However,the distribution within the habitats used by GPS-tracked immature gulls the year after theAnthropopause appeared to have been reduced compared to the previous years. Our resultsdemonstrate the sensitivity, the adaptability, and resilience of this opportunistic urban predatorto changes in food availability caused by human activities

25 Congreso Español de Ornitología, 9-13 de noviembre de 2022, Menorca

Peer reviewed