A study by the University of Sussex, published in Science of the Total Environment, has found that there is a high prevalence of veterinary drugs in bird nests.
They analysed 103 blue and great tit nests sent in by volunteers on the Nesting Neighbour Scheme at the British Trust for Ornithology. Researchers screened the nests for 20 different insecticides and detected 17 of them in the fur the birds used to line their nests. The number of insecticides present in each nest ranged from two to eleven. They found fipronil in 100% of the nests and imidacloprid and permethrin in 89% of the nests. Fipronil is banned in the UK for agricultural use and imidacloprid has been banned for use in agriculture since 2018. However, all three pesticides are still widely used in tick and flea treatments for pets.
A blue tit’ s clutch of eggs inside a nest box. Credit YK on Shutterstock.com
The researchers found clear evidence that these insecticides are harmful to birds as there was a higher number of unhatched eggs or dead chicks in nests containing a higher number of insecticides, higher total concentration of insecticides or a higher concentration of fipronil, imidacloprid or permethrin. This suggests that exposure of the eggs to insecticides in the nest linings may lead to mortality and lower reproductive success.
Dr Cannelle Tassin de Montaigu, the lead author on the study, said: “No nest was free from insecticides in our study, and this significant presence of harmful chemicals could be having devastating consequences on the UK’s bird populations.
“Many pet owners leave fur outdoors after brushing their pet, hoping it will be used by birds like blue tits and great tits to line their nests. While this practice may seem harmless and even helpful, our study has found that chemicals commonly used in animal flea and tick treatments (e.g., fipronil, imidacloprid, permethrin) make their way into bird’s nests. These substances, often banned for agricultural use due to their environmental risks, are still widely used in veterinary applications. These can commonly be found in shampoos, sprays, and spot-on treatments for pets and/or livestock.”
Sue Morgan, Chief Executive of Songbird Survival who funded the study, said: “We are a nation of pet lovers and bird lovers, and it is extremely concerning to see the alarming levels of toxic pesticides in bird nests from veterinary drugs. Pet owners will be upset to hear that in trying to do the right thing to support their pets with fleas and ticks, they could be harming our ecosystem, resulting in dead newborn chicks and unhatched eggs. As pet owners, we need to have confidence that we are keeping our pets well, without devastating impacts on our wildlife.
“Our UK songbirds are in crisis. More than half of our UK songbirds are threatened or already in decline, which is why this latest research shows the importance of taking action as soon as possible. We want the government to undertake a more comprehensive environmental risk assessment of veterinary drugs.”
You can read more about the impacts of pet tick and flea treatments in our guide here.
