Untangling the role of a novel agroecosystem as a habitat for declining farmland birds

Abstract

As a result of agricultural industrialisation, traditionally managed habitats have dramatically declined throughout Europe. As a result, farmland specialists across several taxa have become increasingly threatened. Concurrently, altered farming practices have also contributed to the emergence of novel agricultural habitats, such as Christmas tree plantations, but knowledge of their impact on biodiversity is still scarce. In the following study, we analysed the drivers behind the territory selection of four declining farmland birds-Common linnet (Linaria cannabina), Tree pipit (Anthus trivialis), Woodlark (Lullula arborea) and Yellowhammer (Emberiza citrinella)-in a landscape dominated by Christmas tree plantations. Our study suggests that Christmas tree plantations provide well-suited breeding conditions for the species and thus may represent important refuges in human-modified landscapes. We found that all four species favoured young Christmas tree plantations (<6 years) for territory establishment. In particular, the territories of Tree pipit and Woodlark were characterised by a high proportion of young plantations, which provide open habitat structures rich in bare ground. However, older plantations (>6 years) were also of high importance for some of the model organisms, especially for Common linnet and Yellowhammer. The territory establishment of Yellowhammer was additionally favoured by brushwood plantations, clear-cut/fringe vegetation and low-growing shrubland. We attribute the high value of Christmas tree plantations mainly to the coexistence of open habitat structures rich in bare ground and less intensively managed stands, which both represent important foraging sites for the model organisms. At least in intensively used agricultural areas, Christmas tree plantations may represent important refuges for declining farmland birds. Therefore, further measures aiming to promote habitat quality while reducing the use of herbicides in the plantations should be addressed.