Pesticide Contamination Moves Through the Food Web, From Aquatic Insects to Terrestrial Birds and Bats

(Beyond Pesticides, May 15, 2026) As water bodies continue to be contaminated by pesticides and fertilizers used in chemical-intensive agriculture, international researchers find increasing threats to both aquatic and terrestrial food webs with insect transmission of pesticide residues from water to land. Published in Environmental Pollution, the study authors analyze insect species with complex life cycles “with an aquatic phase as larvae and a terrestrial phase as winged adults when they serve as prey for many aerial insectivores, such as bats and birds.” As the researchers explain, these insects act as vectors, transferring pesticides from water bodies into terrestrial food webs. As a result of studying feces from birds and bats that prey on these insects, the authors find residues of 16 current-use pesticides, two legacy compounds, and six metabolites (breakdown products).

The study results illustrate that pesticide contamination occurs through the ingestion of contaminated prey from aquatic systems, as all of the substances recovered in the fecal samples are detected in the water bodies within the study region. The transfer of pesticides from emerging insects to other species in the food web further threatens biodiversity and ecosystem functioning. In summary, the authors state, “Our study is among the first to assess multiple pesticide contamination of three aerial insectivores that potentially feed on aquatic insects after emergence, thus the transfer of pesticides via emerging insects needs to be acknowledged as a critical contamination route in the agricultural landscape.”

These residues are noted in barn swallows (Hirundo rustica), Western house martins (Delichon urbicum), and common noctule bats (Nyctalus noctula). In contrast, the researchers did not find pesticide residues in samples from the European starling (Sturnus vulgaris), which is a species that is known to feed primarily on terrestrial insects that do not have aquatic life cycles. This highlights how pesticide contamination in aquatic systems can impact various species throughout the food web and lead to bioaccumulation.