Passerine abundance and diversity in a polluted oasis habitat in south-eastern Tunisia

Abstract

Gabes region, in south-eastern Tunisia, is nowadays considered as one of the most remarkable pollution hotspots in the Mediterranean due to the emissions of the Gabes-Ghannouche factory complex of phosphate treatment. However, because of the lack of detailed studies, the impact of such pollution on the terrestrial wildlife inhabiting this area still remains unknown. In this work, we checked whether the proximity to Gabes-Ghannouche factory complex was associated with a decreased abundance of passerines breeding in the neighbouring oasis habitat. Overall, passerine abundance was found to decrease in the proximity of the factory complex, but this decrease was more pronounced in insectivorous species than in granivorous ones. The latter species seemed to be more dependent on vegetation structure. Moreover, we found that in the sites close to the factory complex, the studied passerine community was dominated by the Sparrow Passer domesticus × hispaniolensis, which seemed to be the less sensitive species to pollution. However, in the more distant sites, passerine abundance was more equitably distributed among species due to the increase in the densities of pollution-sensitive ones. Our findings give support to those reported in polluted European forest habitats and stress once again the usefulness of passerines as reliable biomonitors of polluted terrestrial environments.