Veterinary Insecticidal Compounds in Bird Nests? Researchers Make a Surprising Discovery in Great Tit Nest Boxes

The researchers analysed nest material collected from both urban habitats and protected forest sites. In the animal hair recovered from the nests, they detected several insecticidal active ingredients commonly used against fleas, ticks and other ectoparasites, including fipronil, imidacloprid and permethrin. Veterinary medicinal products containing these compounds have been developed to protect companion animals and livestock from parasites, as well as the diseases they transmit. However, far less is known about their effects on wild birds.

The presence of insecticidal compounds in nest material is particularly intriguing because insecticidal active ingredients introduced into nests via contaminated animal hair could potentially benefit birds. Previous studies have shown that biologically active compounds found in certain aromatic plants incorporated into nests, and even nicotine derived from cigarette butts woven into nest material, may help reduce the abundance of nest parasites. This raises the question of whether insecticides carried into nests on the hair of domestic animals protect birds against nest parasites and other ectoparasites, or whether they instead pose a risk to breeding adults and nestlings.

The answer remains unknown. Zsófia Varga-Szilay, who led the study, explains:

"Our study confirmed the presence of several insecticidal active ingredients in great tit nests and, surprisingly, not only in urban environments but also at a protected forest site located far from human settlements. These findings highlight that synthetic insecticides and other pesticides used by humans can enter natural ecosystems through ecological pathways that have received little attention so far. A tuft of pet hair left behind in the garden, for example, may provide valuable nesting material for many bird species. At the same time, it is important to recognise that the active ingredients of products used to protect our pets may also find their way into nest boxes, where they may act as environmental contaminants posing a potential risk to birds."

The study also highlights the need for further research to determine whether these insecticidal compounds affect birds' health, reproductive success and the development of their offspring, and if so, how.