Numeric response of a neotropical raptor to urbanization gradient in central Argentina

Abstract

Human activities, through the development of agricultural and urbanized areas, are considered a threat to wildlife species. However, there are species that can be unaffected or even benefited by these man-made scenarios. This could be the case of the chimango caracara (Milvago chimango), a raptor species that may prove to be highly adapted to anthropogenic modifications of its habitat, requiring more detailed local population information to scientifically support that hypothesis. The aim of this study was to evaluate variation of density of chimango caracara in a urban gradient in central Argentina. During the Austral summer-autumn of 2017, I measured the abundance of chimango caracaras in 148 transects located in urban-suburban-rural urbanization gradients of 19 localities with human populations varying from 483 to 103,000 inhabitants per locality. Detection and density of chimango caracaras in each locality was analyzed as function of urban gradient, climate and number of inhabitants in each locality using a Distance Sampling approach. Urbanization and climate affected both detection and density. The selected model predicted the highest densities of chimango caracara in suburban, then in urban, and finally in rural habitats (0.18, 0.15 and 0.01 ind/ha respectively). These findings could be the result of the successful process of adaptation of chimango caracara to life in urbanized habitats and indicates that on certain occasions the anthropic disturbance could not be negative in terms of abundance for some species of birds with flexible behaviors.