Abstract

Ecosystem anthropization is a main driver of biodiversity loss, but not all species are equally susceptible. Understanding and preventing biodiversity loss is particularly important in rapidly changing and biodiversity-rich areas like the Neotropics and requires exploring the role of both intrinsic and extrinsic vulnerability drivers. Here, we test how multiple potential intrinsic and extrinsic factors explain vulnerability to extinction in neotropical birds to provide a first insight into what makes these species susceptible to extinction and how they are responding to anthropization. Our analyses included data for 2268 neotropical birds. We characterized extinction risk based on the IUCN Red List categorization and tested the predictive value of seven intrinsic and four extrinsic variables using Bayesian MCMC Phylogenetic Generalized Least-Squares (PGLS) models. As hypothesized, we found higher intrinsic vulnerability to extinction among bigger and more specialized species which have low reproductive output and occupy smaller distribution ranges. Extrinsic drivers were also relevant predictors with more threatened species overlapping largely areas with fewer human activities (lower night light levels and lower human population densities). Our results show that the extinction risk of neotropical birds is correlated with both intrinsic and extrinsic factors. Intrinsic vulnerabilities were as expected associated with narrower, specialized niches and slower life histories. However, risk was not higher in more humanized environments, but instead more at-risk species were found in less disturbed areas that we suggest may represent refuges for birds that previously occurred in wider ranges and have now been excluded from the more anthropized regions. Our results contribute to our understanding of vulnerability predictors in birds and provide a first evaluation of neotropical birds that highlights the complex relationship between human pressure and biodiversity loss.