A fear analogy: the escape response of an urbanite bird in two Finnish cities

Fear response to anthropogenic disturbance can shape species behavior and influence their distribution and population health. Fear is species- and situation-specific, but can be quantified by using behavioral indicators such as alert distance (AD), flight initiation distance (FID), and escape distance (ED). In this study, we collected ADs, FIDs, and EDs of the white wagtail (Motacilla alba) in two cities in Finland, Helsinki and Lahti. We aimed to find whether bird age, sex, flock size, pedestrian activity, distance to refuge, land use, built cover or escape method related to any of the indicators and whether these relations differ by city. For analysis, we used linear models (LM) and classification and regression trees (CART). Flock size had a positive correlation with AD, and distance to refuge had a positive correlation with both AD and FID. Juveniles were shyer, with higher FIDs and EDs. Escapes in Helsinki, and by running were shorter. Additionally, in Helsinki, higher pedestrian presence was positively related to AD and ED, flock size with FID, and in commercial land use, birds escaped shorter distances. In Lahti, there was fewer correlations, so that distance to refuge had a positive correlation with AD, juveniles had higher FIDs, and runners had shorter EDs. Built cover had a non-linear relationship with all indicators. Understanding fear is crucial when assessing how species respond to environmental change. At the same time, it offers tools for modulating animal behavior, be it for conservation or non-lethal deterring.