Assessing the risk of fipronil-treated seed ingestion and associated adverse effects in the red-legged partridge

Fipronil is an insecticide commonly used in agriculture, but there are growing concerns over its environmental impacts (e.g., harmful effects on pollinators). Fipronil-treated seed ingestion might threaten granivorous farmland birds, in particular, Gallinaceous birds that are particularly sensitive to this insecticide. We report here on exposure risk and effects in a game bird of high socioeconomic importance, the red-legged partridge (Alectoris rufa). We fed captive birds with untreated maize (controls) or with a mixture of untreated–treated maize (ratio 80:20; exposed birds) during 10 days at the beginning of the breeding period (n = 12 pairs in each group). We first show that exposed partridges did not reject treated seeds but reduced food intake and lost body condition. We further studied the effects of treated seed ingestion on adult survival, oxidative balance, plasma biochemistry, carotenoid-based coloration, cellular immune response, steroid hormone levels, and reproduction. Fipronil exposure altered blood biochemistry and sexual hormone levels and reduced cellular immune response, antioxidant levels, and carotenoid-based coloration. Exposed pairs also had reduced egg fecundation rate and produced eggs with fewer antioxidants and offspring that had reduced cellular immune response. These negative effects on adult partridges, their reproductive performance, and offspring quality highlight that fipronil-treated seed ingestion is a significant threat to wild birds.The present study was financed by FEDENCA (Real Federación Española de Caza) and Oficina Nacional de Caza with the partnership of Fundacion Biodiversidad.Peer Reviewe