Effect of urbanization on individual condition of a threatened seabird: the Olrog’s Gull Larus atlanticus

Abstract

Urban areas are usually places with increased pollution, abundant parasite communities and other factors that can increase physiological stress affecting negatively the individual condition of organism. Here we investigated the relationship between physiological condition of free-living Olrog’s gulls Larus atlanticus and the level of coastal urbanization. The conservation status of this gull and its recently colonization of urban ecosystems highlights the importance of this study. Sampling was conducted in two coastal sites having a highly different level of urbanization and habitat degradation. Thirty-eight gulls were captured at Mar del Plata and forty-four at Mar Chiquita Reserve (Buenos Aires, Argentina) during the winter of 2016–2019. Biochemical and hematological metrics, and oxidative damage products were analyzed. Uric acid levels, regardless the sex and age, were lower in urban individuals compared to non-urban individuals. Cholesterol levels were higher in males from the urban site. Red blood cell counts were lower and white blood cell counts were higher in urban than non-urban immature individuals. In adults the hematocrit concentration was higher in urban than non-urban individuals. Immature individuals from urban site showed higher heterophils than immature individual captured in non-urban sites. Urban females showed less monocyte concentration than non-urban females. Neither oxidative damage nor the antioxidant capacity were affected by site when nested by age and sex. These results reveal differences in the physiological condition of Olrog’s gulls, and highlight the importance of monitoring species that use large cities and raise important questions about how generalist animals adapt to urban areas.