Cat colonies and flight initiation distances of urban birds: Dealing with conflicting sources of citizen wellbeing

Abstract

Feral cat colonies in cities improve the wellbeing of people who feed and care for them, but they can have negative effects on biodiversity due to the predatory behaviour of cats. We analyse the effect of the presence of the 1171 colonies of feral cats reported for the city of Madrid (Spain) on the flight escape distances (FIDs) of birds to approaching human observers under standardized conditions. Location of cat colonies was obtained from maps maintained by the city authorities. The FID is a behavioural trait that integrates effects on bird's fearfulness of exposure to predation, disturbance, and physiological and reproductive needs. Shorter flight distances are associated with less exposure to predators and disturbance and better access to food and mates. Shorter FIDs are also associated to higher abundances and more positive population trends, at least in Spain. Mean FIDs of 694 birds of 34 species measured in nine city areas in the spring of 2021 were 10% longer in zones with colonies of feral cats than in neighbouring paired zones without colonies but similar regarding other factors potentially affecting FIDs (i.e. urban landscape structure). Birds were 33% higher above ground in zones with colonies, with no significant effects of perching higher on bird fleeing behaviour. Cat colonies were therefore increasing the fearfulness of individual birds and, presumably, downgraded their population trends. Compromising bird conservation with wellness effects of cat colonies on citizens at the city scale will thus imply the maintenance of colony-free areas, especially for ground-foraging birds. In addition, provision of perches for its use as temporal refuges around colonies might reconcile positive and negative effects at local scales.