Veterinary insecticides detected in wild bird nests across urban and forest habitats
A study published on bioRxiv detected multiple veterinary insecticides — including fipronil, imidacloprid, and permethrin — in Great Tit nest materials collected from urban and protected forest sites in Hungary. The compounds, commonly used in flea and tick treatments for pets, likely entered nests via animal fur incorporated into nest linings. The findings identify a previously overlooked pathway by which companion animal treatments may expose wildlife to neurotoxic chemicals, even in protected ecosystems.
Researchers analysed fur-containing nest material from 63 Great Tit (Parus major) nests in artificial nest boxes at an urban site and a nearby protected forest in Hungary during the 2025 breeding season. Using HPLC-MS/MS and GC-MS analytical methods, they detected fipronil, fipronil sulfone, imidacloprid, permethrin, and acetamiprid — several of which are restricted in EU agriculture due to environmental concerns but remain permitted in veterinary products. Acetamiprid was found exclusively in urban nests, suggesting additional non-veterinary contamination sources in cities. Urban nests showed higher contamination levels and greater compound diversity than forest nests, though residues were detected at both sites and at both sampling points — mid-nestling stage and post-fledging — declining over the breeding cycle. Importantly, no statistically significant association was found between contamination levels and the reproductive parameters measured in the birds. The authors argue the results reveal a poorly recognised environmental pathway linking widespread pet treatment products to wildlife exposure, and call for ecological risk assessments of veterinary insecticide use.
What's missing
The study is a preprint and has not yet undergone peer review. The authors acknowledge that no reproductive effects were detected, but the study was not designed to assess sublethal neurological, behavioural, or long-term fitness effects in adults or nestlings. Actual exposure doses absorbed by birds — as opposed to residue concentrations in nest material — were not measured. The study covers a single breeding season at two sites in Hungary, limiting geographic and temporal generalisability. The specific pet treatment products responsible for contamination were not identified.
What different sources said
- bioRxivCenter
Veterinary insecticides in wild bird nests: emerging contaminants in urban and protected forest habitats
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