Greenfinches & “Fat finch” disease (Trichomonosis)

November 14, 2010

in A selection of my garden wildlife videos, Birds, Gardening For Wildlife, Wildlife

Why are greenfinches dying in my garden?

This question and Where are the Greenfinches?, I am asked on a regular basis. This article and my presentations/talks sheds light as to why this is happening and suggests preventative measures we can, as part of responsible wild bird feeding practices, help to minimise the spread of this killer disease.

NB.  Uneaten food around the bird’s beak is a likely source for contamination for other birds

Trichomonosis or ‘fat finch’ disease… updated

For the past two years at my new address the greenfinch population has been devastated by what I suspect is avian trichomonosis. Many people call it ‘fat finch disease’ a very apt description. In the UK, it first appeared in greenfinches visiting gardens in the summer/autumn 2005, as a result of the Citizen Science scheme, Garden BirdWatch, run by the British Trust for Ornithology, (BTO). It is a well known disease called ‘canker’ in pigeons and ‘frounce’ in raptors. Pigeons and doves may be the main carriers.

The infection is the result of a parasitic organism, called Trichomonas gallinae. Last summer I had about 15 greenfinches visiting all at once, reducing to a handful over the winter months. This spring/summer (2010) 7 birds visited gradually reducing to none now (Oct 2010). I have always had greenfinches visiting on a daily basis. Nationally it has been estimated that in excess of half a million greenfinches have died. Considering that the UK greenfinch population is about 4 million birds, this is a huge reduction.

I don't like using graphs! This is an exception though!

I don’t like using graphs! This is an exception though!


Greenfinches, Chaffinches, Goldfinches, House sparrows, Bullfinches can be infected. Although it is Greenfinches that have been affected the most.The poor infected birds look lethargic, weak, sleepy, fluffed up, have difficulty breathing, are reluctant to fly, hang around bird feeders and attempt to eat. They physically cannot swallow food or drink. Unfortunately food or water does not reach their stomach due to the ‘cheese‘ like lesions in the bird’s crop, caused by the parasite. The parasite itself feeds upon cell debris, pus and bacteria as found in the birds crop. As the disease progresses, birds may drool and have uneaten food on the beak with matted, wet plumage around the face and beak. The birds eat yet starve to death or die of thirst. You can often see them stretching their necks to probably to help with their discomfort. It could be described as the myxamotosis of the bird world.

It is heart breaking to see greenfinches with this disease in your garden knowing that you may be responsible for the birds catching it. In my garden, it is mostly greenfinch males that catch the disease, as they have a more dominant position at bird feeders than females. In fact it could be argued that the more dominant birds are more likely to die of trichomonosis because they are more dominant and therefore more likely to eat contaminated food. Thus the more dominant traits in breeding male greenfinches could be lost as they die from the disease along with their dominant genes, with females being forced to mate with less dominant males, or at least there could be an imbalance in male/female numbers. However that is a case for further research!!

How it spreads

As Trichomonosis cannot live for long outside of its host, especially where there is no moisture, it is generally transmitted through very close host-to-host contact. So sharing food and water resources offers a good transmission route. One method of infection  is passed on from one bird to another by feeding regurgitated food. For example greenfinches feed their offspring with regurgitated seeds whereas wood pigeons feed their offspring via pigeon milk. It is also spread by sick birds which are unable to swallow food. Infected birds will spit out food, or it drops from their beak. The infection is found in the saliva or in faeces so it is very easy for other birds to pick up the infection from any infected foods as they feed at feeders, bird tables or on the ground. Infected birds drinking from bird baths and thereby infecting the water is also likely to be another transmission route along with faecal transmission on food or into water as they bathe. Courtship rituals, are another potential transmission route, whereby  a male bird offers a food parcel to his mate. The higher concentration of birds at feeding stations, increases the spread of the infection. In 2010 I wrote to the BTO about Trichomonosis and its spread. Mike Toms(BTO) replied. 

A potential source of infection for our bird visitors

A potential source of infection for our bird visitors


I recently revived some information from a Greenfinch and European Goldfinch breeder, for which I am grateful as it informed me about how breeders treat it and prompted me to update this article! He told he treated his sick birds with Ronidazole, which I note is used for Trichomonosis in pigeons and birds. This may well work for captive birds, which are easily isolated and treated away from the other birds.

“I put one teaspoon in 1 quart of water and give it to the birds affected fresh every day for 5 days. It works excellent.
I raise green finches and european gold finches and when they get sick this is my first treatment.
It is hard to administer on wild birds.
I just had a sparrow sick and I caught him and treated him.
Best if you can catch the sick bird. Normally they cannot fly and treat them in cage.
You can put some medicine in a bath you give and hope the sick  birds drink”.


Personally, I would not use medication for wild birds. I have no knowledge of medication, treatment or otherwise of this product. I am not a vet! How can you measure the right dose for effective treatment of a free living wild bird under field conditions that may feed for a very short period before it flies away, without receiving the full medication dose? If it only receives a small dose, its possible the organism may become resistant to the medication. The wrong treatment may be taken by the wrong bird and could kill it. This may well be treatable in captive birds or racing pigeons, but wild free living birds. I don’t think so. So what can we do? If possible, prevention is better than treatment.


I feed the birds for my pleasure and to help them. I don’t want to be killing them, right? As such I feel I have a responsibility to provide the birds with a safe environment and use safe feeders in which they can feed.

Importance of feeding hygiene

This is were hygiene becomes very important. Feeders includes all feeders including hanging trays, tables and ground feeders. My bird feeders are regularly cleaned with an environmentally friendly disinfectant and boiling water. Then left to air dry and stored. Another clean feeder stored in the garage is then used, so I alternate them frequently. Prior to having a wildlife pond made, I changed the bird bath water on a daily basis, again allowing it to air dry before refilling with fresh water. A simple old paint tray is useful for a bird bath, works a treat and makes use of something that just sits unused in the garage!

Bird bath. Simple, effective and cheap

Bird bath. Simple, effective and cheap

Prevent contamination around bird feeding/bathing stations

Look beneath your feeder and you will likely see bird droppings, seeds and other materials. Over time this can build up and hold moisture. Trichomonosis can survive in such conditions long enough to infect other birds that may feed/search amongst this material.

Regularly move your feeders around the garden helping to eliminate this buildup. Remove the built up material and bin it. Failing that you could pour boiling water on it killing the organism. Be aware though that on soil, grass etc, this will likely kill other organisms near the soil surface such as earthworms.

Have different types of feeders to suit different species and place them around your garden, thereby spreading the numbers of birds in your garden and limit the overcrowding in small spaces.

Wear rubber gloves when cleaning, other organisms may be present, e.g. Salmonella.

Clean feeding stations regularly depending upon how dirty they become.

Place bird bath or water bowls away from bird feeders, bird tables or other areas where birds perch. This will help reduce faecal contamination or bird food spat out by an infected bird landing in the water.

Ground food should be placed in a different area of the garden on a daily basis.

Keep surfaces on which birds feed clean. I spray my squirrel baffle with an eco friendly disinfectant.

As Woodpigeons (numbers visiting gardens has markedly increased in recent years, esp. in early summer when food gathering for their young) are carriers, it may be prudent to keep them away from feeders or ground tables. A range of products are available and you can also devise your own methods.

If you get a large number of birds at your feeding station and you fear the spread of this disease or you see an infected bird, the Garden Health Wildlife advice that you stop all feeding altogether for 2-4 weeks. This will make the birds disperse. Although likely the birds will find other feeders where these hygiene methods are not practiced.

Mouldy food may contain toxins which may cause disease in birds and harbour other infective organisms. e.g. Salmonella.

Keep food store dry and away from rodents. Mine is kept in a large galvanised metal refuge bin.


If you see an infected bird, then feeders and table should be cleaned daily.

Spray your bird feeders with an eco friendly disinfectant on the outside and around the perches, where food debris and faeces may contaminate food morsels.


It may be right that I undertake these precautions but I still get infected birds. If people in my vicinity do not do likewise, these simple hygiene methods may not be adopted simply through lack of knowledge. This message needs to get to a wider audience, hence this article!

If you would like to take part in this valuable citizen science wildlife recording programme, Garden Bird Watch scheme whilst sitting in the comfort of your favourite armchair then see below……

“All my articles AND videos, GIVEN TO YOU FREE, are funded by my  teaching and sales of award winning bumblebee nest boxessolitary bee boxes,  and wormeries. Please help by spreading the word and forwarding this link to your friends and colleagues.

Thank you” George Pilkington

Refs and further reading

Infectious Diseases of Garden Birds- Minimising the Risks

Garden Wildlife Health download PDF 

Report disease outbreaks here…

Trichomonosis has spread to Finland

BTO Population trend graphs

For a detailed description of the Trichomonosis organism 

Emerging infectious Disease Leads to Rapid Population Declines of Common British Birds

Join BTO Garden BirdWatch…..

{ 34 comments… read them below or add one }

Peter Rigby November 14, 2010 at 9:58 pm

Dear George – absolutely brilliant – whoever thought we would both end up carrying out such two diverse careers after all we have BOTH been through!! Keep up the great and excellent work my friend. See you Thursday – Peter R.


Lynda February 1, 2012 at 10:37 am

Dear George, last evening we found a greenfinch in a distressed state ?we had monitored it all day & watched it get weaker until it didn’t attempt to fly away.Because it was so cold & snowing we brought it in to keep it warm intending to let it go today,sadly it died last night & reading the info you provided the symptoms were that of trichamonis.We feed a lot of birds daily & always ensure daily clean water & their dishes & tables cleaned frequently.Is there any thing else we should be doing.We had this problem last year in the spring when one died then.Do you think it’s trichamonis .Thanks .Lynda ,South Wales.


nurturingnature February 1, 2012 at 4:10 pm

Dear Lynda, I will get back to you.Bye for now, George


nurturingnature February 2, 2012 at 4:00 pm

Dear Lynda, I contacted Dr. Tim Harrison BTO, on your behalf, as I felt you were doing everything you could do. He sent me this reply….” By keeping food fresh and cleaning bird baths/feeders regularly, Lynda is essentially doing everything she can. Of course, the birds might be contracting disease from elsewhere, so there is something to be said for having the ‘cleanest restaurant in town’. If the problem persists, however, it would be sensible for Lynda to stop feeding for a short while (e.g. a week or two – certainly until no more diseased birds are seen), get everything really clean, then start again.

The other important thing to do is to tell the BTO about diseased birds through our simple online survey: Through this, important information is shared with a vet, Becki Lawson, at the Institute of Zoology, who is taking a lead in this research. You can contact Becki by emailing Lynda – Becki would like to hear from you if you have the Greenfinch’s body available for post-mortem (this is the only way to confirm cause of death, e.g. trichomonosis).

HTH, bye George


Lynda February 2, 2012 at 5:05 pm

Dear George, thank you very much for your reply.I have completed the
Online survey,however we disposed of the bird & therefore I don’t see
any point contacting Becci,should this occur again I will keep the birds
body & contact her for what to do next.
My husband pointed out to me that we had a Feral Pigeon which had
been a regular visitor to our garden for 2yrs ,this also identical symptoms to the Greenfinch,however we thought at the time it had died of old age.I have also completed info on that death online.
Once again thank you for your help .
Lynda, S Wales.


nurturingnature February 3, 2012 at 8:09 am

Lynda, my pleasure!


Murphy July 21, 2014 at 11:32 am

Just found a second green finch this week with these symptoms. We had this two years ago when we found three dead birds. Is the disease on the increase again?


nurturingnature July 21, 2014 at 10:32 pm

Try the BTO web site for the latest news on that. George


jackie march April 12, 2015 at 1:07 pm

I AM SO EXCITED!!! I have a single Green Finch on my feeder…


nurturingnature April 12, 2015 at 6:03 pm

Jackie, you are very lucky and I can see why you are excited! I used to see 12-15 every day. Now I may see 1-3 every few months….thanks for sharing! Cheers, George


Amanda Huddleston September 5, 2015 at 8:17 pm

We have a sick greenfinch hanging round our garden. It has been around for 2 weeks and seems to be improving. Is it possible it may survive?


nurturingnature September 5, 2015 at 9:57 pm

Hi Amanda, There are other avian diseases that are not fatal to birds so hopefully it will survive. Thanks for sharing. Cheers, George


Sue Slater October 19, 2015 at 1:58 pm

We have a big fat greenfinch in our garden that appears to fit the description of having this disease with food round its mouth, only saw it yesterday for the first time. Its been eating at the feeders and been in the pond. Only flying away when about 4 ft away, our Lab has not even bothered it. I stopped mowing the lawn so as not to disturb it. Then came in to look it up as its was so much bigger than the others. Heart breaking as we have so many other finches and tits come. Hope it doesnt devistate the population. I will remove all food and clean my feeders.


nurturingnature October 19, 2015 at 9:52 pm

Its a sorry sight to see Sue. WE think we are helping the birds and we may well be spreading this awful disease because we don’t keep our feeders, bird tables and areas around the feeders clean. Moving feeders every week, cleaning acc will help. Thanks for sharing. George


vivienne January 17, 2016 at 10:27 am

I live in east Sussex and used to see Green finches
in my garden until about 5 years ago but they have all gone presumably this awful disease is the cause.Is it possible there might be a come back here,and where in the country have they been spotted.


nurturingnature January 18, 2016 at 3:48 pm

I have very few here nowadays. The population has crashed nationally by about 1/3, so it may take some time to build up numbers again, providing more don’t die off. Cheers, George


Karl June 20, 2016 at 9:22 pm

I’m glad I found this webpage as I watched a greenfinch die in my garden this evening. It was puffed up like a ball and matched all the symptoms you listed. I will certainly give my feeders a good clean and be more regular at doing so. I love these colourful characters and would hate to think I could be helping this disease spread. I will share this useful information with my friends who have feeders. Thanks for the great page.


nurturingnature June 21, 2016 at 7:50 pm

My pleasure Karl. Please do spread the word! Thanks, George


eric September 3, 2016 at 8:17 am

Over the last two weeks i have found three g/finches dying or dead,thanks for this page i now know what it is .


nurturingnature September 3, 2016 at 6:29 pm

Hope you can persuade your neighbours to clean their feeders! Cheers, George


Jaruzelski jackson October 4, 2016 at 9:08 am

Found several green finches dead or dying in my garden, will they recover in numbers


nurturingnature October 4, 2016 at 8:27 pm

It appears that there are not recovering yet. Keep your feeders clean and send people to this site to be made aware of this killer. George


Hilary Davies October 4, 2016 at 11:54 am

We have found 8 green finches dead in our garden in the last two weeks. Heartbreaking. We have been on this website and realise this is the same problem. We keep our feeders cleaned and bird bath not sure about neighbours . We have had pigeons and doves a lot in our garden.what can we do apart from not feed birds anymore.? We have so many different birds. This is really a dilemma for all.We live in Wiltshire not come across this before.


nurturingnature October 4, 2016 at 8:25 pm

Check out the Guardian bird feeding cage,keeps out larger birds the ground feed HTH George


Sally Sadler November 5, 2016 at 4:14 pm

I have a poorly green finch. Its not fat just normal but cold. I’ve got it to drink water and left it near an electric heater with food and water in my green house. Is there more I need to do. I’ll check all my feeders but I normally only get starlings and sparrows! I found it on the lawn and picked it up. It was clinging to me and felt warm compared to me but it snuggled against me. I think it’ll be dead by morning.


nurturingnature November 6, 2016 at 11:15 pm

Very difficult to say Sally. It could be suffering shock from a cat attack, injured or have fat finch disease. I hope it survives. I wrote about some medication RANIDEZOLE that could be given to a bird with fat finch disease, it may be worth reading up on that if it survives the next day or so. HTH, George


Sally Sadler November 7, 2016 at 9:17 pm

Update. Sadly the finch died. There’s nothing obvious although I’ve kept it and will look more closely. My immediate thoughts were it was dehydrated and I noticed its beak wasn’t clean. Perhaps it had been regurgitating? I will pluck it and look for damage as I did think it could be shock. I’ve met the sparrow hawk twice! It flew into me last summer!


nurturingnature November 8, 2016 at 10:04 pm

Yes sounds like its tricho. As they cannot swallow food or drink sufficient water because the organism in the crop stops it going to the birds stomach.I would bury it 6 inches deep in the garden. Thanks for sharing, George


Jan Johnstone December 13, 2016 at 7:49 pm

We have had diseased greenfinches in the garden from time to time recently. We also have regular visits from the sparrowhawks .Could you tell me ,please, if the disease can be transmitted to the hawk if it eats an infected finch?


nurturingnature December 14, 2016 at 11:33 pm

Hi jan, I believe it would take quite a few for this to happen.. Thanks for sharing look up frounce re birds of prey. HTH G


Jan Johnstone December 15, 2016 at 9:44 am

Thank you for the advice.”Founce” ,as a term ,is new to me. The information on the website was very useful, particularly about the need to dry out all the feeding /watering equipment in addition to disinfecting.
I’ll need a spare set of everything now.
Well Christmas is coming.


nurturingnature December 19, 2016 at 9:00 pm

That’s how I get my feeders Jan!! Cheers, George


john longbottom February 20, 2017 at 4:29 pm

I am not quite sure who I am speaking to (George?) but nevertheless hi.
Read the article with interest. We have just lost 4 greenfinches in the space of 4 days. One at the back of the house, another around the front of the house (panting heavily or seemed to be) and two today directly under the bird feeder. We have feed birds for 35 years and have had no issues. We recently bought a new feeder that has a base and a surround to keep the food in and we noticed the food lies in water after heavy rain (so I drilled four holes in the base to allow evacuation). We feed the birds sunflower seeds peanuts from different feeders and fat balls – and here I think lies the problem. I followed your advice and I am ashamed to say I collected about 5 kilos of food from the garden floor that was congealed because of the fat that had fallen. We have decided to give up on fat balls since they do not seem to last. We live in France and the quality of fat ball is not the same. In the UK they never broke up (but times could change) but here once they are reduced by 50% they just fall apart on end up on the floor. We thought nothing of it because we could see other types of birds feeding on the ground.
Also you mention different types of birds like different types of feeders. Have you any information on this? We used to live in the Auvergne in central France and we could have 20 different species of bird in the garden feeding at the same time. The diversity was amazing but alas here in Brittany we do not have the same variety Thanks John


nurturingnature February 23, 2017 at 12:56 pm

Will email you John. Cheers, George


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