© Marcel Burkhardt
Ugolini, P. (2018)
Effects of pedestrians on behaviour of Turdus merula.
Master thesis. University of Basel, Swiss Ornithological Institute
Human encounters with wildlife during recreational activities increased massively over the last decades. Previously undisturbed habitats are now being visited by humans. Birds possibly perceive human as predators. Hence, they alter their physiology and behaviour during an encounter with humans. The extent of the physiological and behavioural reactions and their possible negative consequences are quite complex and not well known yet. This study investigated the short-term effects of a low-threshold anthropogenic disturbance on the behaviour of breeding common blackbirds (Turdus merula). Common blackbirds, equipped with PAM-loggers, were disturbed experimentally by pedestrians walking along the hedge they were breeding in. The PAM-loggers measured acceleration in the z-axis with a frequency of 6.25 Hz. The acceleration data was correlated to observations of the birds’ behaviour. The three different behaviour types flight, activity and inactivity could be determined. The amounts of each behaviour before, during and after a disturbance event were then compared. Pedestrians did evoke a sex- and status-dependent change in behaviour of breeding common blackbirds. Incubating female birds increased their flight behaviour, whereas feeding females decreased their activity and were more inactive in response to the disturbance. Feeding male birds showed only a slight increase in flights. These results can be explained by the sex- and status- specific tasks during the reproduction period. A change in behaviour was still visible after the disturbance event. Especially the incubating females increased their amount of inactivity during the 30 minutes after the disturbance event substantially, suggesting that low-threshold disturbances might also have long-term or even fitness consequences. A combination with the data from the Vhf-transmitters, conducted at the same time, will give some more insight into the temporal and spatial pattern of the reaction of those common blackbirds and might allowing to draw some general conclusions about the impact of pedestrians on common blackbirds.
key words: Human disturbance, low-threshold disturbance, PAM-loggers, acceleration, behaviour determination