For the study, which was funded by the charity Songbird Survival, researchers collected the nests of 103 blue and great tits, and tested them for the presence of 20 insecticides.
Fipronil, imidacloprid and permethrin were the main culprits, detected in 100%, 89.1% and 89.1% of the samples respectively.
Overall, a higher number of either dead offspring or unhatched eggs was found in nests containing a higher number of insecticides, higher total concentration of insecticides or a higher concentration of fipronil, imidacloprid or permethrin, which the authors say suggests contact exposure of eggs to insecticides in nest lining may lead to mortality and lower reproductive success.
The BVA responded by calling for more research and encouraging vets to work with clients to ensure responsible use of parasiticides.
BVA President Elizabeth Mullineaux said: “Parasiticides play an important role in preventing and treating parasites in animals, which if left unaddressed can lead to bigger health and welfare issues in both animals and people.
"But it’s important they are used responsibly, and this work from the University of Sussex and SongBird Survival highlights the need for more research into how parasiticides affect the environment and wildlife and the associated risks.
“Rather than blanket use, we strongly encourage vets and owners to take a risk-based approach to prescribing or recommending these medicines, reflecting an animal’s exposure to parasites."
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