Urban pigeons losing toes due to human activities

Measuring the impacts of urban pollution on biodiversity is important to identify potential adaptations and mitigations needed for preserving wildlife even in city centers. Foot deformities are ubiquitous in urban pigeons. The reasons for these mutilations have been debated, as caused by frequenting a highly zoonotic environment, by chemical or mechanistic pigeon deterrents, or by necrosis following stringfeet. The latter would mean that pigeons frequenting pavements with more strings and hairs would be more exposed so subject to mutilations. We tested these hypotheses in Paris city (France), by recording the occurrence and extent of toe mutilations on samples of urban pigeons at 46 sites. We hypothesized that mutilations would be predicted by local overall environmental conditions, potentially related to local organic, noise or air pollutions, so gathered such environmental predictors of urban pollutions. We showed that mutilations do not concern recently fledged pigeons, and that their occurrence and frequency are not related to plumage darkness, a proxy of a pigeon's sensitivity to infectious diseases. Toe mutilation was more frequent in city blocks with a higher degree of air and noise pollution, while it tended to increase with the density of hairdressers. In addition, the number of mutilation on injured pigeons was higher in more populated blocks, and tended to decrease with increasing greenspace density, and to increase with air pollution. Pollution and land cover changes thus seem to impact pigeon health through toe deformities, and increasing green spaces might benefit bird health in cities. Toe mutilation in urban pigeons is linked to human-induced pollution.