I have received an increasing number of calls over recent weeks from garden birdwatchers concerned at the appearance of dead and dying finches. In most instances these reports have involved greenfinches and chaffinches but there have also been occasional reports involving other species. This is not the time of the year when we would normally see birds dying from common diseases like salmonella and e-coli (these are normally seen in late winter), which suggests a different source. Thanks to the efforts of researchers working on the Garden Bird Health initiative, we have discovered that the disease involved is trichomonosis. This disease is caused by a parasite and it has been documented in a range of bird species, most commonly in doves and pigeons (where it is more commonly known as ‘canker’). The disease was first recognised in finches in Britain last summer, when a small outbreak was noted but this summer the outbreak seems to be that much larger and this has caused some concern.
Individual birds showing signs of the disease appear lethargic, fluffed up and reluctant to move away from feeding stations. They may have difficulty swallowing and may drool saliva or regurgitate food, something which can cause the feathers around the bill to become wet. Although in captivity the disease can be treated, it is virtually impossible to treat wild birds with an effective dose of medication. This means that prevention is the only practical option and garden birdwatchers should aim to reduce the risk of disease transmission between birds by adopting sensible hygiene practices. These include keeping bird feeders and bird tables clean (with a disinfectant or detergent) and by insuring that clean, fresh water is available each day, provided in vessels that have been thoroughly cleaned. It has been suggested that you should stop feeding altogether if you find any sick or dying birds but I feel that it is better to feed birds at a clean feeding station than force them to move on and potentially feed elsewhere where no hygiene measures are in place.
Most of the reports that I have received so far have come from western and central England but we should be alert here, in Norfolk, to the possibility that the disease might arrive. The parasite itself cannot survive for long outside of the body and it appears to be transmitted through salival contamination of food and water. This may be why it has been more widespread this summer – with the dry conditions reducing the availability of drinking pools and forcing more birds to congregate at those which remain. More information on the disease and on sensible hygiene measures can be obtained from the British Trust for Ornithology and UFAW.