Responses to the black locust (Robinia pseudoacacia) invasion differ between habitat specialists and generalists in central European forest birds

Biological invasions are among the most important threats to global biodiversity. However, bird species differ in their ability to resist the invasions, and it is thus important to investigate which species’ traits account for their sensitivity to the invasions’ consequences. Here we focused on predictors of such sensitivity by using central European birds in oak forests invaded by the exotic black locust (Robinia pseudoacacia). We performed a detailed mapping of bird occurrence on plots located in the native oak stands and the invaded stands, respectively, controlling for stands’ age. Using multivariate analysis, we quantified bird species’ reliance on the native versus invaded forest stands. In the next step, we tested the hypotheses explaining species’ position along this gradient. We predicted that the species more closely associated with the invaded forest stands will be (1) habitat generalists and (2) species with fast life history strategies. The phylogenetic generalized least squares analysis showed that only the first prediction was supported. Moreover, species’ habitat specialization significantly affected differences in species’ abundance between the invaded and native forests: habitat generalists were more abundant in the black locust stands than in the oak stands, which was not the case of habitat specialists. Our study implies that the spread of invasive plants may contribute to the frequently reported replacement of specialist species by habitat generalists in local bird communities.