Greenfinch Welfare and Trichomonosis Disease

Greenfinch populations have crashed by over 60% due to trichomonosis, a protozoan disease spread at garden feeders that causes fatal throat lesions preventing birds from eating.

Key Facts

Greenfinch populations declined by 63% in the UK between 2005 and 2020
Trichomonosis is caused by the parasite Trichomonas gallinae, spread via saliva at feeders
Infected birds develop yellowish throat lesions causing difficulty swallowing
Affected greenfinches appear lethargic, fluffed up, and regurgitate food
The disease was first recorded in UK garden birds in 2005
Chaffinches are also affected, though greenfinches are most severely impacted

Welfare Considerations

Trichomonosis causes significant and prolonged suffering in greenfinches. Throat lesions grow progressively, making swallowing increasingly painful and difficult. Birds starve slowly while appearing to eat, unable to process food. Death can take days to weeks from infection. The disease spreads through communal feeding stations where birds share saliva on feeder ports. The welfare intervention is clear: rigorous feeder hygiene prevents transmission. Removing feeders temporarily during outbreak periods allows surviving birds to disperse and reduces spread.

What You Can Do

Clean bird feeders thoroughly every two weeks with 5% disinfectant solution
Remove and clean feeders immediately if sick birds are observed
Space feeders widely to reduce bird crowding and disease transmission
Report sick greenfinches to the BTO Garden Wildlife Health project
Plant native shrubs providing natural berries and seeds as feeder alternatives
Spread awareness about trichomonosis and the importance of feeder hygiene