Table of Contents 1. 2. What exactly is Trichomonosis and what causes it?3. When was Trichomonosis first discovered in finches?4. Which species of garden bird does Trichomonosis affect?5. How do birds transmit and catch Trichomonosis?6. How to minimise the risk of Trichomonosis affecting the birds in your garden

It seems likely that most people who feed the birds in their gardens will now have heard about a fatal disease called Trichomonosis which has affected different species of finch, and notably Greenfinch and Chaffinch. Trichomonosis can be found across Europe and can occur both in the wild and in gardens. It’s been discussed at length on BBC’s Springwatch and Winterwatch, with Chris Packham and others quite rightly aiming to ensure a high level of public awareness. But far fewer people will understand what causes the disease, plus the steps that can be taken to minimise the risk to their own garden birds.

What exactly is Trichomonosis and what causes it?

Trichomonosis is caused by the single cell protozoan parasite called Trichomonas gallinae. The parasite causes lesions in the throat of the bird, making it difficult for it to swallow. This leads to lethargic behaviour, with other symptoms including wet and matted plumage around the beak. In the vast majority of cases the disease is fatal. 

 

When was Trichomonosis first discovered in finches?

The disease first emerged in finches in 2005, though it had been known about for many decades before in pigeons and doves, where it is also called ‘canker’, plus in birds of prey where it is called ‘frounce’.

Which species of garden bird does Trichomonosis affect?

The main two species are Greenfinch and Chaffinch, with Siskin and Bullfinch also affected. Goldfinches can also catch the disease, though much less frequently. House sparrows and Tree sparrows have also been recorded with Trichomonosis. From the pigeon and dove family, Wood pigeon, Collared dove and Turtle dove are all susceptible – though unlike for songbirds, the disease is not always fatal.

How do birds transmit and catch Trichomonosis?

The main two ways are through infected dropped food and infected water – e.g. in a bird bath. For the infected food, this happens because a bird with Trichomonosis is generally unable to swallow, and therefore when it tries to eat it will drop food – e.g. seed it’s taken from a bird table – which is coated in saliva and contains the parasite. Another bird may then pick up the infected food, and therefore the disease is transmitted. Equally, an infected bird may try to drink from a bird bath or other water source, with the parasite then transferred to the water which another bird may drink from.

Crucially for both the scenarios described above, the Trichomonas gallinae parasite can live much longer outside of a host bird if its environment is wet – or at least damp. Temperature also plays a role, with warmer conditions allowing the parasite to live longer. This warmth isn’t just weather-related, but can also be at a micro level when bacteria generates heat in damp and decomposing bird food and waste (e.g. seed husks).  So taking the example of a tube seed feeder, if the ports and perches become caked in rotting waste and are also wet or just damp, then this would be an ideal environment for the parasite to remain alive for perhaps a few days. However, if an infected bird dropped food onto the perch of a perfectly clean and dry feeder, then it’s likely that the parasite would live for much less time (perhaps just a few hours).

The issue of dropped food onto a surface which is both unclean and is holding moisture, is why bird wooden tables and other types of feeders with flat surfaces are now considered much more likely to be responsible for transmitting Trichomonosis compared to other types of feeder.

How to minimise the risk of Trichomonosis affecting the birds in your garden

Hygiene is absolutely central, and not just keeping feeders clean but also the ground below them. But there are also various other very important steps you need to take, all of which we’ve detailed in our comprehensive guide.  As a brief summary of what the guide contains:

  • How to keep bird feeders clean and how often you need to clean them
  • Why you shouldn’t use a bird table
  • Why it’s so important to clean up husks and other waste
  • The need to move feeders around your garden very regularly
  • Dispose of uneaten bird food and the main reason it’s likely not to have been eaten
  • Why the new advice is to avoid feeding stations
  • Keeping food and feeders dry
  • Changing water in bird baths regularly and how best to keep the bath clean
  • How you can tell if a bird is sick and what to do if you find one