A multi-biomarker approach to evaluate the ecotoxicological status of great tit (Parus major) populations from areas with different anthropogenic impacts

Multiple anthropogenic pressures can lead to physiological alterations or damages to birds, potentially resulting in cascading effects on individual's fitness and population dynamics. Cavity-nesting birds, such as the great tit (Parus major), provide an excellent model for investigating the effects of environmental stressors on avian species. Their territorial behaviour and the accessibility of their nests make great tits particularly suitable for investigating the environmental conditions of their nesting locations. This study aimed to evaluate the ecotoxicological status of great tit populations inhabiting areas with different anthropogenic impacts, using a multi-biomarker approach. During the breeding seasons of 2021 and 2022, blood and excreta samples were collected from 198 nestlings belonging to 44 nests across four different areas of the Veneto region (northern Italy), representing wood (14 nests), urban (9 nests) and agricultural (9 and 12 nests) environments. Immunotoxicity, oxidative status, genotoxicity and neurotoxicity responses were evaluated on blood, while porphyrins levels on excreta. Results revealed significant physiological alterations in nestlings from urban and agricultural areas (oxidative status modifications, immune response impairments and genotoxic effects), likely associated with environmental stressors typical of anthropized ecosystems. The wood area presented elevated protoporphyrin levels, suggesting unexpected exposure to diffuse airborne particulate matter from nearby cities. The IBR index revealed that populations inhabiting urban and agricultural environments suffered the highest physiological stress. This multi-biomarker approach has proved to be a valid tool for assessing the ecotoxicological status of the great tit populations exposed to different stressors, allowing to be proposed for the conservation of wild bird species.