Abstract
Urban habitats are often dominated by non-native trees, but our understanding of their impacts on birds remains limited. We investigated such impacts by comparing the stands of non-native Robinia pseudoacacia and Pinus nigra, with the stands of native Quercus sp. and Pinus sylvestris.
No reduction of bird species richness in the stands of invasive trees was found. Instead, the stands of the invasive R. pseudoacacia were dominated by habitat generalist birds, while habitat specialists were confined to the stands of native Quercus sp.
Habitat generalists probably benefited from a dense shrub layer in the stands of invasive trees, which was much reduced in the stands of native trees. By contrast, native tree stands most likely provided richer food supply for birds via higher insect biomass and diversity than that found in the invasive tree stands.
We suggest that habitat specialists might thus lack some key food resources in the stands of invasive trees. Plant invasions thus may not always reduce bird species richness, but can significantly alter species composition of bird communities at the expense of ecological specialists.
To prevent such adverse impacts, we urge to plant only native tree species in European cities wherever possible.