Pesticide-coated seeds as a threat to red-legged partridges and other granivorous farmland birds: evidence from studies conducted in Spain

Abstract

The coating of seeds with pesticides is widely used in agriculture, and is increasingly recognized as a significant threat to farmland birds. During the sowing season, spilled and unburied seeds constitute an abundant and easily accessible resource for granivorous animals. Farmland birds may be attracted by, and feed on some of these seeds, with the consequent risk of ingesting large amounts of pesticides in a short time and suffering toxic effects. We review here recent knowledge gathered on risks and effects of pesticide-coated seed ingestion in the red-legged partridge Alectoris rufa in Spain, and present future directions for research on this topic. Experiments conducted on captive partridges exposed to seed coated with fungicides (difenoconazole, thiram) or insecticides (imidacloprid, fipronil) have shown a wide range on effects, from increased mortality to reduced reproductive output, as well as adverse effects on bird physiology and condition. We briefly review these effects, depending on the dose and the chemicals used. We also review information on the palatability and availability in the field of pesticide-coated seeds, and on their prevalence in the gizzard of red-legged partridges hunted in Spain. Finally, we present current research plans aimed at: i) validating biomarkers of exposure using non-invasive methods, ii) refining exposure assessment of wild red-legged partridges through a better understanding of space use and diet, and iii) testing the effectiveness of measures aimed at minimizing the risk of treated seed ingestion by partridges and other farmland birds.