Movement ecology of urban birds: a review of tracking studies

Abstract The world is urbanizing rapidly, impacting the movements of wildlife living within ever fragmenting urban habitats. Movement tracking by biologgers can reveal the nature of these impacts for birds—particularly those that are prevalent within urban environments. We assembled and reviewed 123 studies examining the movements of birds in urban environments using movement tracking. We assumed that avian movements are driven by different internal states, such as foraging or reproduction, and synthesized the literature accordingly. We found that the number of studies per year increased over time, which was accompanied by a significant decrease in the average body mass of studied species over time. However, this was largely driven by studies employing non-satellite biologgers, as opposed to generally more high-resolution satellite biologgers such as GPS (interaction t130 = 3.50, p 0.001). Furthermore, a tendency towards the study of structurally larger dietary-generalist species (e.g. Laridae spp.; 31.6% study effort) leaves significant gaps in our movement knowledge of smaller dietary-specialist species. Priority areas for future investigations are thus outlined, including focusing on smaller common urban taxa, such as songbirds generally, which form a significant but understudied proportion of our urban birds.