Behavioral responses of urban birds to anthropogenic disturbance in green areas in Curitiba, Paraná (Brazil)

Proximity to humans can influence behaviors that are essential in a bird’s life, such as breeding, foraging and flight. In urban parks, which are important natural shelters to birds, human activity varies broadly in time such that attentiveness and escape behavior of birds may be intensified when density of humans increases. In this study, we tested this hypothesis in six green urban areas at Curitiba, S Brazil and using three common urban bird species as models, the Rufous Hornero (Furnarius rufus), the Southern Lapwing (Vanellus chilensis) and the Rufous-bellied Thrush (Turdus rufiventris). More specifically, we tested if foraging rate, alert distance (AD), flight initiation distance (FID) and flight distance (FD) are related to the number of humans within a bird’s home range area. Through linear mixed model, we found no influence of humans on birds foraging rate, whereas AD, FID and FD decreased with human density in the bird’s surroundings. We also found differences in birds escape strategy; “flying” strategy was associated with higher AD, FID and FD than “walking” strategy. Results also indicate that bird’s vigilance and flight responses were temporally affected by human presence and apparently reflect a strategy that ensures constant foraging rate irrespective of human density. Our study provides evidence of behavioral plasticity of the model species to the intensity of human use of their living area, which also highlights the importance of further efforts in creating refuges within these urban parks to minimize anthropic impacts on urban species.