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A neonicotinoid insecticide reduces fueling and delays migration in songbirds

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Science  13 Sep 2019:
Vol. 365, Issue 6458, pp. 1177-1180
DOI: 10.1126/science.aaw9419

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Hazardous delays

Neonicotinoids are a widely used group of pesticides that have been shown to have negative impacts on an increasing number of species, most notably pollinators. Eng et al. tested how exposure to these compounds influenced the behavior of a migrating songbird. Ingestion of field-realistic levels of neonicotinoid insecticides reduced feeding and accumulation of body mass and fat stores, which led to delayed departure from stopover sites. Such delays can lead to reduced migration survival and decreased reproductive success and therefore have the potential to impose population-level impacts.

Science, this issue p. 1177

Abstract

Neonicotinoids are neurotoxic insecticides widely used as seed treatments, but little is known of their effects on migrating birds that forage in agricultural areas. We tracked the migratory movements of imidacloprid-exposed songbirds at a landscape scale using a combination of experimental dosing and automated radio telemetry. Ingestion of field-realistic quantities of imidacloprid (1.2 or 3.9 milligrams per kilogram body mass) by white-crowned sparrows (Zonotrichia leucophrys) during migratory stopover caused a rapid reduction in food consumption, mass, and fat and significantly affected their probability of departure. Birds in the high-dose treatment stayed a median of 3.5 days longer at the site of capture after exposure as compared with controls, likely to regain fuel stores or recover from intoxication. Migration delays can carry over to affect survival and reproduction; thus, these results confirm a link between sublethal pesticide exposure and adverse outcomes for migratory bird populations.

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