Declines in insectivorous birds are associated with high neonicotinoid concentrations
Recent studies have shown that neonicotinoid insecticides have adverse effects on non-target invertebrate species. Invertebrates constitute a substantial part of the diet of many bird species during the breeding season and are indispensable for raising offspring. We investigated the hypothesis that the most widely used neonicotinoid insecticide, imidacloprid, has a negative impact on insectivorous bird populations, based on long-term and country-wide standardized monitoring schemes on pesticides and bird populations in the Netherlands.
Local population trends of 15 insectivorous bird species were significantly more negative in areas with higher surface-water concentrations of imidacloprid, with populations declining by 3.5 per cent on average annually above concentrations of 20ng/l. This spatial pattern of decline appeared only after the introduction of imidacloprid to the Netherlands, in the mid-1990s. Additionally, the negative relationship remains after correcting for spatial differences in land-use changes that are known to affect bird populations in farmland. Our results suggest that the impact of neonicotinoids on the natural environment is even more substantial than has recently been reported and is reminiscent of the effects of persistent insecticides in the past. Future legislation should take into account the potential cascading effects of neonicotinoids on ecosystems.