Wild Greenfinch Decline: Disease, Garden Feeding, and Recovery

The greenfinch has suffered dramatic population declines due to trichomonosis, a parasitic disease transmitted at garden feeding stations, illustrating the welfare risks of high-density supplementary feeding.

Key Facts

Greenfinch populations in the UK have declined by around 63% since 2005, largely due to trichomonosis outbreaks
Trichomonosis is caused by the parasite Trichomonas gallinae and causes lesions in the throat that prevent swallowing
The disease spreads at garden feeding stations where birds share contaminated food and water
Finches appear unwell: lethargic, fluffed up, and unable to swallow; the condition is almost always fatal without treatment
The BTO monitors trichomonosis through the Garden Bird Health scheme and sick bird surveys
Regular cleaning of feeders and bird baths with 5% disinfectant solution is the most effective preventive measure
Some birds appear to develop resistance; populations show partial recovery in areas where disease has been present longest
The parasite also affects chaffinch and other finches; the implications for broader finch welfare are significant

Welfare Considerations

The trichomonosis epidemic in greenfinches illustrates how well-intentioned wildlife feeding can create welfare harms when feeder hygiene is neglected. Birds dying of trichomonosis experience throat obstruction and starvation over several days - significant suffering. The preventive solution is straightforward: clean feeders weekly with disinfectant, remove uneaten food regularly, and move feeding stations periodically. The BTO's public education campaign on feeder hygiene has raised awareness, but compliance remains incomplete. Garden bird feeders are a national welfare intervention at enormous scale; making feeder hygiene routine is a genuine public health measure for wild bird welfare.

What You Can Do

Clean bird feeders and bird baths weekly using 5% disinfectant solution followed by thorough rinsing
Remove uneaten seed and food debris regularly from feeding stations
Move feeders to different locations periodically to reduce ground contamination below stations
Report sick or dead greenfinches and finches to the BTO Garden Bird Health scheme
Share information about trichomonosis and feeder hygiene with other garden bird feeding enthusiasts