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.
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.
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.
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.
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!
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……
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Refs and further reading
Report disease outbreaks here…
For a detailed description of the Trichomonosis organism
Join BTO Garden BirdWatch…..http://www.bto.org/gbw/