Neonicotinoids: Still present in farmland birds despite their ban

Neonicotinoids (neonics) are the most widely used insecticides worldwide and are considered to be of low risk to non-target organisms such as vertebrates. Further, they are reported to be rapidly excreted and metabolized, reducing their potential toxicity. Nevertheless, growing evidence of adverse effects of neonics on farmland bird species raise questions about the purported harmless nature of these pesticides. We attempted to search for pesticide residues in species of different trophic levels and at different life stages, by using multiple bird monitoring programs on a Long-Term Socio-Ecological Research (LTSER) platform. Three passerine birds-the blackbird (Turdus merula), cirl bunting (Emberiza cirlus), and common nightingale (Luscinia megarhynchos)-that feed on seeds and invertebrates were monitored during their reproductive period, and the grey partridge (Perdix perdix) that feeds on seeds was monitored during its wintering period. We also monitored chicks of an apex predator-the Montagu's harrier (Circus pygargus)-that preys mostly upon common voles but also upon insects. We found that the birds' blood samples showed presence of residues of five neonics: three banned since 2018 in France-clothianidin, thiacloprid, and thiamethoxam-and two-dinotefuran and nitenpyram-used for veterinary purposes only. While none of these neonics was detected in blackbirds, all were present in grey partridges. Clothianidin was detected in all species, except blackbirds. Concentrations of the three banned neonics were similar or higher than concentrations found in birds monitored elsewhere before the ban. These findings raise questions about the persistence of neonics within the environment and the mode of exposure to wild fauna. Future investigations on the sublethal effects of these neonics on life-history traits of these farmland birds may help in providing a better understanding of the effects of exposure of bird populations to these insecticides, and also to the consequent effect on human health.