Ecological specialization and population trends in European breeding birds
Federico Morelli, Yanina Benedetti, Corey T. Callaghan
Abstract
Successful conservation strategies depend on the correct identification of animal species and populations at a higher risk of extinction. But not all species are equally sensitive to environmental changes. Specialist species are often considered more prone to extinction than generalist species. However, even considering the importance of the link between specialization and population trends of species (a potential proxy for extinction risk), only a few studies have provided evidence supporting this relationship. Here, we tested whether the population trend of breeding birds in Europe is linked to a specific category of species’ specialization, using continuous measures of avian specialization based on a trait-approach. We focused on five different indices of avian specialization: diet, foraging behavior, foraging substrate, habitat selection, and nesting site selection. We calculated the mean value and the standard deviation of the population trend for 139 bird species. Then, we tested for the presence of a phylogenetic signal in bird population trends, in order to investigate if the tendency for related species to resemble each other, often demonstrated regarding phenotypes, is present also for the species’ trends in Europe. We found evidence that bird species with negative trends were characterized by higher ecological specialization than species with positive trends. Specifically, population trends were negatively associated with nesting site specialization. We highlight that the species’ degree of specialization can be used as a proxy for that species’ ability to adapt and persist to environmental changes. Finally, the lack of a phylogenetic signal in either the mean value or standard deviation of the bird population trend suggests that the current status of a species is not strongly associated with the degree of phylogenetic relatedness.