Research Project

Do veterinary drugs harm nesting tits?

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In recent years, we’ve become more aware of the environmental impact of chemicals. Spot-on flea treatments for domestic pets, like those containing pesticides such as fipronil, have been found in rivers across England.  The impacts on songbirds and wildlife are relatively unknown.

Research shows that over 85% of dog owners used a flea-treatment in the last year. Of these, 36% claimed to let their dog to swim in rivers or streams at least once a month.  While we know these treatments end up in water, we don’t know how much further they travel and where they can end up.

The Project

Building on the findings of the birds and pesticides research, SongBird Survival is continuing to build the relationship with the University of Sussex by funding the 'Do veterinary drugs harm nesting tits?' project. The project will be done in collaboration with Dr Julia Schroeder at Imperial College London using Silwood Park as the site*.

In January 2024 Dr Cannelle Tassin de Montaigu began a 2-year postdoctoral research project, to explore if spot-on flea treatments could have an impact on the breeding and survival of nesting tits.  

Many species of songbird use dog, cat and livestock hair in their nests, often as cushioning before laying eggs. This project hypothesises pesticide treated pet and livestock hair could be present within nests, potentially affecting eggs and chicks.

Research goals:

Using the Imperial College London site at Silwood Park*, this study will:

  • Test for pesticides in the linings of nests and unhatched eggs collected during the previous  birds and  pesticides project.
  • Provide both pesticide-treated wool (with fipronil) and untreated wool to blue and great tits for nest-building.
  • Monitor blue and great tit nest boxes to record hatching success, survival rates, and biometric data.
  • Test nests for parasites and pesticide residues at the end of the breeding season.

*The blue tit project at Silwood Park operates under the Home Office Project Licenses of Dr Julia Schroeder: PPL 7009092: Sept 2016-Sept 2021 and PPL PP5873078: Sept 2021-Sept 2026.

Coloured (treated) wool in tree, photo by Cannelle Tassin de Montaigu

The Results

This research project is still ongoing, but here are some initial results from the project so far:

  • 103 nests were collected from blue tits and great tits and tested for pesticides.
  • 100% of nests were contaminated with fipronil (used in spot-on flea treatments for domestic pets).
  • 89.1% of blue tit nests and 87.2% of great tit nests had detected levels of imidacloprid (also used in spot-on flea treatments).
  • 89.1% of blue tit nests and 84.6% of great tit nests had detected levels of permethrin (typically used in anti-parasite treatments for livestock).
  • The highest concentration of substance found was dinotefuran at 7,198ppb, which is also commonly used in flea and tick treatments for domestic pets for dogs/cats.
  • For all blue tit and great tit nests together, a higher number of dead offspring and unhatched eggs were found in nests with a higher insecticide concentration.

The Solutions

Based on the results that have come out so far, we can see that veterinary drugs do appear to have an impact on nesting tits. We are calling for greater environmental risk assessment of veterinary drugs by the Veterinary Medicines Directorate to assess their impact on all wildlife and the environment.

We are a nation of pet lovers and many pet owners will be using the ‘spot-on’ flea treatments for cats and dogs as they look to keep their pets well.  Many pet owners will be very concerned to hear that these veterinary drugs are potentially having such a negative impact on songbird populations. This is why we need a greater environmental risk assessment of what pesticides are used in veterinary drugs.

Please talk to your vet about the best flea treatments for your pet and how often they should be used to help protect your pet, people, and the planet.  

As recommended by the British Veterinary Association, pet owners and vets should have informed discussions about their pet’s flea and tick treatments, to risk-assess when treatments are needed, taking into account animal, human and environmental health risks, in addition to lifestyle factors. This can give the opportunity to avoid blanket year-round flea and tick treatment.

SongBird Survival recommend:

  • If you do continue to use these treatments, do not brush your dogs or cats outside or put out hair for the birds to use in nest making.
  • Not allowing pets in rivers and streams following the application of spot-on flea treatments.
  • If you choose to use a flea treatment, consider oral/tablet options, available from your vet; these may have a lower environmental impact.
  • To protect the environment, it’s important to use flea and tick products correctly. Always follow the instructions on the product leaflet and apply the treatment to your pet as directed. Pets shouldn’t swim, be bathed, or go to the groomers for a few days after the treatment, preferably for as long as possible (up to 28 days).
  • Make sure to dispose of the packaging properly in household waste and use the product only on the species listed.

Meet our scientists

What is a Songbird?

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Professor Dave Goulson

Supervisor - UNIVERSITY OF SUSSEX

Professor Goulson studies the ecology, behavior and conservation of bumblebees, with an interested in pollinators and pollination more generally, and particularly in the sustainable management of pollinators in agro-ecosystems. .

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Dr Cannelle Tassin de Montaigu

Postdoctoral researcher - University of Sussex

Cannelle is a post-doctoral researcher at the University of Sussex, specialising in ecotoxicology and conservation ecology. Her current research focuses on the impact of veterinary drugs (such as spot-on dog treatments) on the health of nesting tits.

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OUR PUBLICATIONS

Tassin de Montaigu, C., Glauser, G., Guinchard, S., Goulson, D. (2025) High prevalence of veterinary drugs in bird's nests. Science in the Total Environment. https://doi.org/10.1016/j.scitotenv.2025.178439

RELATED STUDIES

Perkins, R., Goulson, D. (2023) To flea or not to flea: survey of UK companion animal ectoparasiticide usage and activities affecting pathways to the environment. PeerJ. 11, 15561, 10.7717/peerj.15561

Perkins, R, Whitehead, M, Civil, W., Goulson, D. (2021) Potential role of veterinary flea products in widespread pesticide contamination of English rivers. Science of the Total Environment. 755: 143560

Wells, C., Collins, C.M. (2022) A rapid evidence assessment of the potential risk to the environment presented by active ingredients in the UK’s most commonly sold companion animal parasiticides. Environmenta Science and Pollution Research. 29: 45070-45088.

See our publication library for more of our research.

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