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Trichomonosis in finches and other garden birds

Greenfinch infected with trichomonosis

Large numbers of greenfinches are dying of a disease called trichomonosis

Image: Bill Ironside

Since summer 2005, trichomonosis, a disease caused by a microscopic parasite has been reported in finches in gardens. Since then, outbreaks have been seen every year during the late summer and autumn.

They have been studied by the Garden Bird Health Initiative, of which the RSPB is part (see below). Greenfinch populations have been recorded dropping by a third, and chaffinch populations by a fifth in those parts of the country that suffer the most serious outbreaks.

Research published in September 2011 shows that the disease has since spread to finches on continental Europe, most likely with migrating chaffinches.

Which birds are affected?

Greenfinches are reported most frequently, but other finches and house sparrows are also susceptible to trichomonosis. Formerly, it was seen in pigeons and doves and some birds of prey. This is a disease found only in birds - it does not pose a threat to the health of humans, cats or dogs.

What happens?

The trichomonad parasite lives in the upper digestive tract of the bird, and its actions progressively block the bird’s throat, making it unable to swallow food. The bird dies from starvation.

Birds with the disease show signs of general illness, for example lethargy and fluffed-up plumage, but affected birds may also drool saliva, regurgitate food, have difficulty in swallowing or show laboured breathing.

Finches are frequently seen to have matted, wet plumage around the face and beak, and uneaten food in and around the beak. In some cases, swelling of the neck may be seen from a distance.

How is it passed on?

The trichomonad parasite is vulnerable to drying out and cannot survive for long periods outside the host. Transmission of infection between birds happens when they feed one another with regurgitated food during the breeding season, and through food or drinking water contaminated with recently regurgitated saliva.

What can I do?

If trichomonosis is suspected, it is recommended to temporarily stop putting out food, and leave bird baths dry until sick or dead birds are no longer found in the garden.

This is to discourage birds from congregating together, which may increase the potential for the disease to spread between individuals.

Wild birds can suffer from a variety of diseases from time to time. Good hygiene practice, specifically the regular cleaning of all feeders, bird baths and feeding surfaces, is an essential part of looking after garden birds and will help to lower the risk to birds of diseases in general.

No effective treatment can be administered to birds in the wild, because it is impossible to ensure that the infected individuals receive an adequate dose and that healthy birds do not pick up the medicine. Also, a positive confirmation of the disease is needed prior to starting any treatment, and this can usually only be obtained by a post mortem.

The Garden Bird Health Initiative

The Garden Bird Health initiative (GBHi) was set up as a UFAW (Universities Federation for Animal Welfare) Working Group in 2003, including among others the RSPB, the BTO, and the Institute of Zoology.

In 2005, the GBHi was extended to become a major research and surveillance project studying garden bird health and disease outbreaks. This unique combination of scientists, conservationists and wildlife vets has proved to be a very successful partnership.

The group develops and publishes guidelines about how to best feed garden birds in order to maximise the benefits for their welfare and conservation, and minimise the risks from infections. It also researches into the impacts disease outbreaks can have on bird populations.

How you can help

If you are finding sick and dead birds in your garden, please help us monitor the spread and intensity of all disease outbreaks in garden birds by telling us what is happening to the birds visiting your garden. You can access a recording form by clicking on the link to the right.

Thanks for your contribution to this valuable piece of monitoring work. We're sorry, but when we receive a lot of enquiries, we may not be able to respond to each one personally.

Diagnosis of disease, including trichomonosis, in wild birds relies on post mortem examination. The GBHi recommends following sensible hygiene precautions as a routine measure when feeding garden birds, and to avoid handling sick or dead wild birds directly.

If you require further information or advice, please e-mail our Wildlife Enquiries team at or call 01767 693690 (Monday to Friday, 9 am to 5 pm).