Trichomoniasis is the condition caused by Trichomonas gallinae – a protozoan (unicellular) parasite. This parasite has been around for a long time – causing ‘canker’ in pigeons and doves, ‘frounce’ in birds of prey, and is even thought to have been a problem for the dinosaurs.

In recent years it has been seen to cause disease in finches – mostly Greenfinch, Chaffinch and Goldfinch. It has been speculated that the increase in the number of pigeons in gardens brought them into closer proximity with finches than they otherwise would have, providing the opportunity for the parasite to transfer and adapt to a new host (i.e. finches). Following initial reports from the UK in 2005, it has established itself in finch populations across Ireland and many European countries. There is no practical treatment for wild birds with trichomoniasis and it nearly always proves fatal within a couple of weeks.

There is no risk to humans, though we always recommend washing your hands after handling and cleaning feeders.

The birds most susceptible to trichomoniasis are Greenfinches and Chaffinches, though other species (particularly finch species) may also be affected.

The parasite makes it difficult for birds to eat, initially leading to difficulty swallowing but as birds struggle to eat they will become colder and less energetic, with symptoms worsening over several days. Infected birds will be inclined to fluff up their feathers more and be slower than other birds to fly away when disturbed. They often have bits of food stuck around their bill. Unfortunately, the bird will eventually succumb to the infection, so the best thing to do is minimise the risk of other birds getting sick.

See below for an image of a Greenfinch with noticeable signs of trichomoniasis.

Unfortunately there is no practical treatment for wild birds. Though medicines do exist for captive birds infected with the parasite, there’s no way to ensure a wild bird receives a suitable dose. Providing the medicine in an uncontrolled way (i.e. in a garden) would also likely create the conditions for a resistant strain of the parasite to evolve and develop, with disastrous consequences for wild bird populations.

If you see a bird in your garden that is likely infected with trichomoniasis, the best thing to do is to remove all feeders and water dishes. They should be cleaned thoroughly with a suitable disinfectant or mild bleach solution (5-10% solution), rinsed and allowed to air dry. The consensus amongst bird conservation experts is that it’s best to then stop feeding or providing water in your garden for two to three weeks. This allows the birds that normally congregate in your garden to disperse more widely in the countryside and means they are less likely to encounter a sick bird. If you keep feeding, you’re attracting the sick bird, other infected birds not yet showing symptoms, and healthy birds, into close proximity, and this will undoubtedly cause the rest of the flock to become infected.

We realise it may seem counterproductive to stop feeding your garden birds completely, but while removing feeders and water may have a temporary and minor negative effect, the birds will die if they contract trichomoniasis, so the further spread of the infection should be avoided at all costs.

After the two weeks are up, gradually reintroduce your feeders one at at time every few days, keeping an eye out for any more sick birds. It’s best to avoid putting out water for another few weeks.

The parasite is transmitted between birds via their saliva, typically at shared food and water sources. It cannot live long outside a host, but can persist longer in damp conditions.

To minimise the spread of infection it is important to clean all feeders and water dishes thoroughly on a regular basis (i.e. at least every two weeks). Feeders should be cleaned with a suitable disinfectant or mild bleach solution (5-10% solution), rinsed thoroughly and allowed to air dry fully before being used again. If you have ‘spare’ feeders it can be good to rotate these when cleaning (i.e. use different feeders every two weeks, giving you plenty of time to clean and dry them).

Other tips include:

• Use several feeders in different locations in your garden, so that all birds aren’t congregating in a single place.
• Change the locations you put your feeders every few weeks, to prevent a build-up of droppings in any one place.
• Use feeders with mesh or drainage holes, to avoid a build up of moisture.
• Change the water in baths daily.
• Where possible, sweep up droppings and any old food and dispose of it carefully.

Yes – trichomoniasis has had a very devastating impact on Ireland’s Greenfinch population in a few short years.

The Irish Garden Bird Survey has proven important in documenting their decline since trichomoniasis arrived. In the 1990s and early 2000s. Greenfinches were recorded in around 90% of Irish gardens each winter. Since winter 2008/09 their numbers have fallen considerably and by winters 2016/17 and 2017/18, they were only in 70% of gardens. The average size of flocks also dropped considerably, from peak counts of 7 birds visiting gardens each winter in the late 1990s, to average peak counts of only 3 birds in recent years.

The Irish breeding population of Greenfinches is monitored each summer through the Countryside Bird Survey and Greenfinch are now at around half the levels they were when the survey began in the late 1990s.

The dramatic declines seen in Irish Greenfinches is reflected in similar declines in the UK and Europe, where trichomoniasis has taken hold. Other finch species, most notably Chaffinch and Goldfinch, also suffer from this infection. Chaffinch numbers in the UK took a brief dip when trichomoniasis initially appeared, but they have largely recovered since. Goldfinch numbers have been on the rise for the last two decades in Ireland and further afield, and thankfully trichomoniasis has done little to slow that increase.

Each year we run the ‘Irish Garden Bird Survey‘ as a way to monitor the health and status of Ireland’s garden birds. The survey runs from December to February each winter and this year, we are asking participants to record whether or not they noticed any finches in their garden that may have been suffering from trichomoniasis. From a scientific point of view, it’s important that we hear what gardens didn’t have sick finches, as well as those that did, to build an accurate picture of the extent of the problem.

If you haven’t taken part in the Irish Garden Bird Survey before, please consider doing so this year. The survey is easy, very enjoyable, and provides us with really important information to monitor and protect our favourite birds. The Irish Garden Bird Survey page on our website has all the details about taking part.