Habitat-dependent variations in the incidence of Chaffinches Fringilla coelebs with diseased legs

ABSTRACT Chaffinches Fringilla coelebs are unlucky in being probably the species most susceptible to diseased legs, either from knemidocoptic mange, Fringilla papilloma virus, or both. In the fourteen winter periods (October to March) 2005/06 to 2018/19 during normal ringing operations I caught 2282 Chaffinches in Cheshire and 86 of those birds were recorded with disease visible on one or both legs. The incidence of diseased legs was significantly higher at feeding stations, where 29 birds were affected out of 186 caught (15.6%), than at sites in farmland (13 of 754, 1.7%), at woodland roosts (34 of 1109, 3.1%) or in my garden (10 of 165, 6.1%). Most of the affected birds were released unringed, without processing, but the age was recorded for 60 of them (56 adults and four first-years); the very high proportion of adults has not been reported before and suggests that visibly affected legs could take a long time to develop, and that birds can live with the symptoms of disease for a considerable time.