Love your pet, love the dawn chorus

Introduction

The dawn chorus, that so many early risers cherish, is facing a new threat. A recent study conducted at the University of Sussex has found a link between the death of songbird chicks and the use of pet fur in their nests. Professor Dave Goulson has released a concise and easy to understand summary of the research on YouTube.^[1]

So, what is going on here? It turns out that the chemicals used in flea drop-on treatments for domestic pets have been found in 100% of nests tested in a recently published study.^[2] The soft fur of our pets, coveted and lovingly transported by songbirds to weave into their nests, is likely driving up songbird chick mortality rates. These findings come hot on the heels of research that indicates the same chemicals are poisoning aquatic ecosystems as well.^[3] Insects such as dragonflies and mayflies are being poisoned, killing them and probably affecting bird, bat and amphibian species further up the food chain.

It’s difficult, as a wildlife loving pet owner, to know how to strike the balance between looking after our furry family members and protecting the wildlife around us. Fortunately, there are some easy steps to take, that benefit pets, people and nature. The checklist flier at the end of this article summarises the easy changes we can all make – changes that could save us money, safeguard the health of our pet families, as well as protecting wildlife wellbeing in our shared urban areas.

Chemical breakdown

The main chemicals of concern found in pet flea treatments are the neonicotinoid imidacloprid and the related chemical Fiprinol.^[4] Neither break down quickly in the environment and both are highly toxic to insects and seemingly songbirds. The agricultural sector, with strict environmental and health standards regulation, has banned the use of neonicotinoids in farming. Following the advice of the health and safety executive and government scientific advisory body, controls are being tightened further, as evidenced by the government decision to revoke exceptions for sugar beet in 2025.^[5]

A nation of pet lovers

Professor Dave Goulson explains that regulation affecting the domestic pet market has been laxer than the controls governing the agricultural industry. This is because in the 1970’s it was deemed that the environmental risk posed by the industries associated with domestic animal welfare, was negligible. However, several factors have given cause to review this assessment: Firstly, the pet population has grown significantly with an “estimated 13 million dogs and 12 million cats living in homes” in the UK. Secondly, there has also been a dramatic increase in spending on “veterinary and pet services, which constituted almost four billion British pounds in 2020”.^[6] Finally, the understanding of how chemicals affect ecosystems and human health has evolved significantly.

The need for action is especially pertinent in urban areas where pet populations are concentrated. 

Toxic danger?

The understanding of fipronil and imidacloprid effects upon animal and human health is still emerging. Most testing has found there is a low risk to animals as a direct result of skin application and “the EPA (US environmental Protection Agency) has determined fipronil to be safe for use on dogs and cats, and it is not harmful to humans who handle these animals if proper precautions are taken.”^[7] However, with a WHO classification of Class II: moderately hazardous, significant illness can result from consumption of the chemical as a result of self-grooming (or mutual grooming if pets live together) and overdosing by applying the wrong amount for the type and size of animal. Symptoms include fatigue, convulsions and difficulty breathing.^[8] The MSD veterinary manual also points out that intentional or accidental consumption by humans can be fatal. For this reason, think carefully about where they are stored so that accidental ingestion can’t occur.

Further evidence has shown that regular application of the flea treatments can cause a build up of the chemical in the home. “Researchers at the University of Sussex and Imperial College London have found that pet owners using flea treatment on their pets, risk contaminating their hands with toxic pesticides for at least 28 days after the treatment has been applied.” ^[9] The chemicals can also be transferred to clothing and upholstery. Several studies acknowledge the uncertainty for human health associated with environmental exposure to these chemicals, though it is commonly accepted to be a low risk. In a US study ^[10] the authors conclude that the chemicals could “pose a risk for mild, temporary health effects in various body systems,” and as such recommend that “precautionary actions should be reinforced to prevent fipronil exposure to product users.”  Another study ^[11] from 2019 identified that “Fipronil sulphone placentally transfers to the fetus.” They do acknowledge that this is very early-stage research and further follow up investigation is required.”

Conclusion for urban wildlife

The British Veterinary Association (BVA) acknowledges the environmental risks posed by flea treatments. ^[13] They advise that vets should be careful to explore the risk factors of each individual home including the presence of elderly and children. In particular, they direct practitioners to “avoid a blanket approach; tailor products and frequency to the animal’s needs and level of risk.”

In areas of dense urban pet populations, it is essential for us all to consider how we might reduce the transfer of chemicals to the rivers and nests surrounding our homes. The easiest way to achieve this is to look at how often we dose our pets with chemicals. We don’t treat our children every month for knits just in case, and taking a precautionary approach to fleas is equally unnecessary.

So, as pet lovers and nature lovers – I urge us all to think about how we apply flea treatments. Do we need to blanket treat? Or, is it possible to only treat when we notice our pets have an infestation instead? There are many potential benefits to making such a simple change: less risk of ill health from contamination; reduced monthly outgoings, and we can all continue to enjoy the dawn chorus!

Please circulate the information flier at the end of this article on social media.

References

1. Goulson. Neonicotinoid Latest News, YouTube. [Link: Neonicotinoid Latest News – YouTube]
2. Tassin de Monatignu et al. High prevalence of veterinary drugs in birds nests, Science of the total environment, Vol. 964, 2025. Link
3. Preston-Allen et al. Are urban areas hotspots for pollution from pet parasiticides? Grantham Institute Briefing Note no. 15, 2023. Link
4. Hunter. Summary of Product (Fiprinol) characteristics, DEFRA product information database, 2023. Link
5. Department for Environment, Food and Rural Affairs. Decision: Statement of reasons for the decision on the application for emergency authorisation of the use of Cruiser SB on sugar beet crops in England in 2025, Gov.uk, January 2025. Link
6. Statista Research Deaprtment. Pet ownership in the United Kingdom (UK) 2012-2023, Statista.com, February 2024. Link
7. C Gupta & R.B Doss. Phenylpyrazole (Fipronil) Toxicosis in Animals, MSD Manual Veterinary manual, September 2024. Link
8. Junquera. IMIDACLOPRID: SAFETY SUMMARY for VETERINARY use in Dogs and Cats. Poisoning, intoxication, overdose, antidote; Parasiterpedia – veterinary parasites, July 2021. Link
9. Perkins et al. Down-the-drain pathways for fipronil and imidacloprid applied as spot-on parasiticides to dogs: Estimating aquatic pollution, Science of the Total Environment, Vol 917, March 2024. Link.
10. Soo-Jeong Lee et al. Acute illnesses associated with exposure to fipronil–surveillance data from 11 states in the United States, 2001-2007, National Library of Medicine, August 2010.
11. Young ah Kim et al. Distribution of fipronil in humans, and adverse health outcomes of in uterofipronil sulfone exposure in newborns, International Journal of Hygiene and Health, Volume 222, April 2019, Pages 524 – 532. Link.
12. British Veterinary Association (BVA). Responsible use of parasiticides for cats and dogs, BVA website, 2025. Link