Are treated seeds an ecological trap for birds?

Presentado al Society of Environmental Toxicology and Chemistry (SETAC) Europe 26th Annual Meeting, celebrado en Nantes (Francia) del 22 al 26 de mayo de 2016.Due to reductions in winter food resources, newly sown cereal seeds have become a key component of many bird species’ diet, but these seeds are often treated with pesticides that may cause toxic effects. In order to complete an appropriate risk assessment, data on treated seed toxicity need to be combined with information about the risk of exposure of birds in the field. The aims of the present work are to characterize the exposure of farmland birds to pesticide-coated seeds in the wild, and to estimate the risk of poisoning of animals as a consequence of such exposure. To do this we analysed crop and gizzard contents of hunted partridges (n=189) to detect residues of pesticides used for seed treatment. Moreover, we measured the contribution of cereal seeds in the winter diet of partridges in order to assess the potential risk of exposure to pesticide-treated seeds. We also studied the abundance of pesticide-treated seeds available for birds in the field (n=48), the pesticides and their concentrations in these treated seeds, and the bird species that feed on them. Seed availability was influenced by the sowing method and the location within the field. Regardless of the sowing technique, there were more seeds on the surface in the headland (43.4 ± 5.5 seeds/m2) than in the field centre (11.3 ± 1.2 seeds/m2) (t151=-4.67, p< 0.001). Six pesticides, mostly fungicides, were detected in the seeds collected from recently sown fields. 55.2 % of the seed samples contained detectable levels of pesticides, with tebuconazole being the most frequently found active ingredient. During the sowing period, 31 species were observed feeding on sown cereal seeds. We detected pesticide residues in the digestive content of 32.3% of the analysed red-legged partridges, including insecticides in a 3.7% of the analysed samples and fungicides in a 29.6% of them. As observed in seeds, tebuconazole was the most frequently detected pesticide (19.1% of the samples). Winter cereal seeds represented a 53.4% of the biomass found in the digestive content of red-legged partridges. The present study demonstrates that the use of pesticide-treated seeds constitutes an important way of exposure of farmland birds to pesticides, and that there exists a potential risk for these birds to suffer toxic effects from ingestion of treated seeds in the wild.Peer Reviewe