Boldness of Urban Australian Magpies and Local Traffic Volume

Abstract

In order to successfully colonise the urban environment, birds must be able tolerate pedestrian and vehicle proximity, because exhibiting a strong fleeing response each time that a harmless traffic stimulus is encountered would be maladaptive. We examined whether a native ‘urban adapter’, the Australian magpie (Cracticus tibicen), varied in its tolerance of human approach and a simulated vehicular traffic sound in urban Melbourne, Australia as a function of pedestrian or vehicular traffic volume in the local area. The flight initiation distance (FID) paradigm and presentation of a potentially startling sound stimulus (SSS) were used to measure the magpies’ boldness in areas with differing traffic volumes. Magpies in areas with relatively high pedestrian traffic volumes exhibited a shorter FID to, and retreated a shorter distance from, an approaching human than conspecifics experiencing relatively low volumes of pedestrian traffic. Magpies in areas with a relatively high vehicular traffic volume were less likely to flee from a SSS than conspecifics in areas with little or no vehicular traffic. Habituation to human disturbance and/or adjustment of anti-predator effort seem the most likely explanations for these disparities and suggest that magpies have considerable behavioural flexibility. The ability to tolerate high volumes of traffic and the associated noise allows magpies to use: (a) ecologically suitable habitat adjoining city roads with heavy vehicular traffic and (b) urban areas with many pedestrians and consequently much human food waste, which the birds exploit.