The effects of neonicotinoid seed treatments on farmland birds

Neonicotinoids are the most common group of agricultural insecticides used worldwide, with seed treatments accounting for a large proportion of applications. Since neonicotinoids were introduced to the agricultural market, concerns have been raised regarding their effect on non-target organisms, and in the last 5 years avian-related research has gained momentum. However, the extent and impact of neonicotinoid exposure in free-living birds, particularly farmland communities, remains poorly understood. Here, data were collected for agricultural plant material and multiple species of farmland bird from neonicotinoid-treated fields, to assess the exposure pathway associated with seed treatments. Biological samples were obtained from 15 species of bird to measure levels of exposure and data were collected to investigate whether there were associated physiological sub-lethal effects. Long-term data sets for neonicotinoid use and bird populations were also modelled to assess the impact of seed treatments on farmland bird species over the last 21 years. Seed treatments were found to be a significant source of exposure for farmland birds. Exposure was confirmed in 9% of individuals pre-sowing, compared to 68% of individuals post-sowing, and 30% of species overall. Exposure was found to be associated with one physiological parameter, which could be detrimental to bird health. There was no consistent evidence to suggest that dietary exposure to neonicotinoid seed treatments has impacted bird populations historically, however three bird species warrant further investigation in this regard. These data suggest that current risk assessment and insecticide product safety protocols do not effectively safeguard farmland bird communities from neonicotinoid exposure during sowing, and imply that exposure may be widespread in bird communities where neonicotinoids are in use. Results obtained here highlight the need for field-based data in ecotoxicological risk assessments and should be considered in relation to any future systemic insecticide seed treatments.