Bird Feeder and Bird Bath Hygiene: How Dirty Feeders Spread Disease

A greenfinch is sitting hunched under your feeder, feathers fluffed out even though it isn't cold, doing nothing. It doesn't fly off as you approach. Its plumage around the bill may be wet, and it looks to be struggling to swallow. If you've seen this, or you've found a dead finch or sparrow near your feeding station, you're most likely looking at a disease that spreads through the feeder or bath itself. Cleaning feeders at least weekly, using retiring flat feeders and pausing seed and peanuts from May to October are the main ways to prevent it.

Trichomonosis and salmonellosis are the two diseases behind most of this. They've reshaped official feeding advice: flat trays and bird tables are out, weekly cleaning is the minimum, and the RSPB and RHS both now advise a summer pause on seed and peanut feeders.

What trichomonosis is

Trichomonosis is caused by a parasite, Trichomonas gallinae, and is often fatal. Affected birds show lethargy and fluffed-up plumage, difficulty swallowing or laboured breathing, and wet plumage around the bill. In pigeons and doves the disease is called canker, and in birds of prey it's called frounce. Greenfinches and chaffinches are the species most often affected, though it has also been recorded in house sparrow, dunnock, great tit and siskin.

It spreads mainly through contaminated food or water, for example where a bird that can't swallow regurgitates food that another bird then eats. The parasite is vulnerable to drying out and can't survive for long outside a bird, which is why regular cleaning breaks the cycle so effectively. The RSPB says the risk of outbreaks is highest in summer and autumn, so a busy feeding station is worth cleaning more often than weekly in those months, perhaps twice a week if it's heavily used.

Trichomonosis first turned up in British finches in 2005, with epidemics in 2006 and 2007. The UK greenfinch population has fallen from about 4.3 million to about 1 million birds, a decline of 77%, and the BTO records a 66% decline in the UK breeding population between 1967 and 2024. Chaffinches have declined since 2012, falling from the second to the fifth most common wild bird species. For chaffinches the drop in survival was more marked in gardens, where supplementary feeding is common, than in the countryside: a direct sign of feeders acting as gathering points for disease when they aren't kept clean.

What salmonellosis is, and why it behaves differently

Salmonellosis in garden birds is caused by Salmonella bacteria, with particular strains of Salmonella Typhimurium responsible for cases in Great Britain. It spreads mainly when infected droppings contaminate food or water. Affected birds look lethargic and fluffed-up, and they often stay around feeding stations, appearing thin.

The critical difference is survival time. Where the trichomonosis parasite dies off quickly outside a bird, Salmonella may persist for weeks to months, longer in favourable conditions. "I'll clean it when I next think of it" is a much riskier approach with this disease: the bacteria don't need a bird to visit today, and can wait for the next one.

Salmonellosis also carries a small human health risk. Of human salmonella cases recorded in England and Wales between 2000 and 2010, only about 0.2% were strains associated with wild birds. No equivalent figure has been published for Scotland, but the way it spreads, through droppings reaching hands or mouth, shouldn't differ north of the border, so treat the figure as a guide to how low the risk generally is, not as zero. If you or a family member develop symptoms after handling feeders or a sick bird, mention that to a doctor. If a cat that hunts falls ill around the time you're seeing sick or dead birds, a call to the vet is worthwhile.

Salmonellosis occurs across Scotland, with a geographic split: finches are most commonly affected in northern Scotland and house sparrows in southern Scotland. A peer-reviewed study of 198 garden bird incidents in Scotland between 1995 and 2008 found the same pattern (Pennycott et al., 2010, Veterinary Record).

The cleaning protocol, in order

1. Empty out old or leftover food. Bin it rather than adding it to a compost heap or scattering it elsewhere, which just relocates the contamination.
2. Dismantle the feeder or bath fully. Take feeders apart into their separate pieces rather than sponging over the outside.
3. Scrub with hot soapy water and a long-handled brush kept only for this job. Damp crusted droppings first, since dry scrubbing can throw fine particles into the air that you don't want to breathe in.
4. Rinse thoroughly.
5. Disinfect with a mild (5%) bleach solution or a non-toxic disinfectant such as Ark-Klens.
6. Rinse again with fresh water to remove all disinfectant from the individual parts.
7. Leave outside to dry completely before you reassemble and refill. A damp feeder put straight back into use undoes much of the benefit. In damp or overcast weather, a sheltered spot with good airflow dries pieces faster than a corner that never catches a breeze, so time the job for a dry, breezy spell where you can.

Keep a dedicated brush and pair of gloves for this job and leave them outdoors, never bring feeder-cleaning equipment into the house, and wash your hands and forearms thoroughly afterwards. Plastic and metal feeders are likely to disinfect more reliably than untreated wood, which can hold moisture and residue in the grain, so bear that in mind when replacing an old feeder.

Shared feeding stations spread disease between other animals too: squirrelpox passes between red and grey squirrels, as covered in red squirrels in your garden.

If you find a sick or dead bird

Act on the first sick bird you see, not just a dead one: by the time a bird has died at the feeder, others visiting the same spot have likely been exposed. Stop feeding at that station and empty any bird baths. The RSPB advises stopping for at least three weeks, and Garden Wildlife Health advises a minimum of two to four weeks, so treat three to four weeks as the sensible default. Leave baths empty for the same period. Resume only once you're no longer seeing birds with signs of disease, do it gradually and keep watching for further casualties. If the problem comes back, Garden Wildlife Health suggests a longer break of three to six months rather than repeating the same short one.

Don't handle a sick or dead bird with bare hands. Use disposable gloves, or a leak-proof plastic bag turned inside out over your hand like a glove. For disposal, gov.wales guidance (the same steps are widely used elsewhere in the UK) is to place the bird in a leak-proof bag, tie it, put that in a second bag, and put it in the normal household waste (a lidded bin outside), taking care not to contaminate the outside of the bag. Alternatively bury it in a hole at least 60cm deep, away from any watercourse. Report what you've seen to Garden Wildlife Health at gardenwildlifehealth.org; their surveillance is built from reports like yours. If neighbours also feed birds, tell them too: the same birds are probably using both gardens, so one clean feeder next door doesn't protect yours.

Bird flu (avian influenza) is a separate and more serious disease with its own official guidance, which can include removing feeders in affected areas. The routine cleaning steps here don't cover it, so check current official advice if you suspect it rather than assuming a few weeks' pause is enough.

Feeder and bath choices that cut disease risk

Retire flat feeding trays and bird tables: the RSPB and RHS both advise this because research shows trichomonosis spreads most readily on flat surfaces, where regurgitated or dropping-contaminated food pools. The RSPB recommends feeders that prevent rain getting in and limit condensation, such as tube and hanging feeders.

A few habits make a real difference. Use several feeders spread around the garden rather than one central point, so fewer birds cluster in one spot. Move feeders regularly (the RSPB and RHS both suggest a different spot each time you put them back after cleaning) so droppings and spilt food don't build up on one patch of ground. Offer only what will be eaten within one to two days, and clear mealworms away by dusk. Avoid siting feeders under roosts or dense tree cover, where droppings from perched birds can fall into the food below.

For bird baths, refill with fresh tap water daily and disinfect weekly. If you can't keep up with that, the RSPB says it's better to leave the bath dry.

On timing, the RSPB and RHS both advise pausing seed and peanut feeders from 1 May to 31 October, when the risk of trichomonosis is highest and natural food is plentiful. Small amounts of mealworms (in a small dish) or fat balls and suet (in a hanging cage) are fine through the summer, and full feeding can resume from 1 November. If you do keep feeding through summer, hygiene matters even more: keep to the weekly clean at the very least, offer small amounts, and stop at once if you see a sick bird.

Which species to attract and what to feed them is on the garden birds page. If grey squirrels are raiding the feeder, hygiene won't solve that: squirrel-proofing a bird feeder is a design fix in its own right.

Common questions

Sources