Fear in urban tropical ecosystems: Flight initiation distance of birds in an urbanization gradient

Abstract

Human-induced disturbances affect animal behaviours such as anti-predatory responses. Animals in urban environments exhibit a reduced escape response, measured as a shorter flight initiation distance (FID), compared to their rural counterparts. While FID has been evaluated in animals in habitats that are completely urban or rural, little is known about how this response vary within urban environments, especially in tropical cities. Here, I studied the FID of resident bird species in Bogota, Colombia, in 22 sites grouped in 3 categories with various levels of vegetation cover and building density (i.e., urbanization gradient) that represented the habitat heterogeneity experienced by urban wildlife. I evaluated whether extrinsic or intrinsic factors affected the escape response. The results showed that birds in larger flocks are more tolerant when being approach, and that the escape response differ between site categories. Birds found in residential areas and urban parks exhibited the shortest FID whereas birds in natural areas exhibited the longest. This indicates that birds in smaller flocks and those in natural areas are less tolerant to human presence than birds found in residential areas and urban parks. Understanding how animals respond to increasing levels of human intervention is important to maintain urban biodiversity.