Research: Declines in insectivorous birds are associated with high neonicotinoid concentrations


Recent studies have shown that neonicotinoid insecticides have adverse

effects on non-target invertebrate species1–6. Invertebrates constitute

a substantial part of the diet of many bird species during the breeding

season and are indispensable for raising offspring7.We investigated

the hypothesis that the most widely used neonicotinoid insecticide,

imidacloprid, has a negative impact on insectivorous bird populations.

Here we show that, in the Netherlands, local population trends

were significantly more negative in areas with higher surface-water

concentrations of imidacloprid. At imidacloprid concentrations of

more than 20 nanograms per litre, bird populations tended to decline

by 3.5 per cent on average annually. Additional analyses revealed that

this spatial pattern of decline appeared only after the introduction

of imidacloprid to the Netherlands, in the mid-1990s. We further

show that the recent 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.

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