Changes in bird communities by planting non-native spruce in coastal birch forests of northern Norway

Abstract

Coastal birch forests in northern Norway have over the last 50 years gradually been replaced with non-native spruce plantations. To investigate possible changes in bird communities, we compared species richness and composition in six forest types (mature spruce plantations, ecotones, mixed forests, and three birch forest types) in two regions over two years. In the southern region, birch forests tended to host a higher number of species than spruce plantations, but species composition differed between forest types. The species composition in rich birch forests was particularly distinguished from spruce plantations, but also from the less productive birch habitats. Furthermore, there were dissimilarities in species richness and composition between regions. Ground nesters and species nesting on their northern margins occurred most frequently in the southern region, whereas cavity-nesters were most abundant in the northern region. Some species declined in abundance from 1998 to 1999, whereas three species shifted their main distribution from birch forests to mixed forests/ecotones. Possible factors underlying these results are discussed. We recommend that researchers and managers pay attention to habitat qualities within forest types (i.e., other than tree species composition in overstory) as well as to regional variations in species assemblages when addressing outcomes of management practices.