Behavioural responses of grey herons Ardea cinerea and great egrets Ardea alba to human-caused disturbance

Abstract. This study examined the effects of different types on anthropogenic disturbance on behaviours of grey herons Ardea cinerea, and great egrets Ardea alba, that gather in an Important Bird Area near Belgrade (Serbia), during their autumn migration, with the goal of assessing how diverse human-caused stimuli affect the behaviours of foraging and resting birds. I obtained behavioural data through scan sampling, with six categories of behaviour distinguished: vigilant, flying, feeding, comfort, inactive and other. In total, I collected 5,065 observations of individual birds: 1,293 for grey herons and 3,772 for great egrets. Significantly more birds were vigilant or in flight when they were disturbed by construction vehicles, military jets, and rural free-ranging dogs, whereas no statistical significance was associated with shooting and passing cars. Using a linear mixed model, it was shown that a greater proportion of birds was vigilant during disturbance than following disturbance or in the absence of disturbance, whereas air temperature and wind speed were not statistically significant. This study demonstrates that anthropogenic disturbance can alter the behaviour of the study species, which could aid future management and conservation planning.