Millions of people feed garden birds; while generally beneficial, poor practice in supplementary feeding can spread disease, create dependence, and harm non-target species.
Garden bird feeding provides welfare benefits through reducing winter food stress and supporting breeding populations, but the risk of disease spread through dirty feeders is a genuine welfare harm. Trichomonosis spread through contaminated feeders has caused significant greenfinch and chaffinch mortality. Regular feeder cleaning, rotation of feeding sites, and use of appropriate food types maximises welfare benefit while minimising disease transmission risk.