Climate and land‐use change drive habitat loss in a mountain bird species

Abstract

Mountain areas still feature remnants of traditional land use and consequently constitute a large proportion of the remaining species‐rich habitats in Central Europe. However, their biodiversity is increasingly threatened by changes in climate and land use. The Alpine Ring Ouzel Turdus torquatus alpestris is a typical mountain bird that has recently declined in most of its breeding range. In this study we compared the historical (1986–1987) and recent (2017) distribution of breeding Ring Ouzels in 62 randomly selected 750 × 750 ‐m plots and analysed local colonization and extinction patterns in 558 subunits (= ‘grid cells’) in the southern Black Forest (south‐western Germany). Our study revealed that habitat occupancy has decreased by about one‐third, mainly at lower elevations and in depressed landforms, during the past three decades. Local colonization amounted to 25% and extinction to 66% of the previously vacant or occupied grid cells, respectively. Habitat occupancy and local colonization and extinction were driven by climate and habitat parameters. The Ring Ouzel preferred convex landscape formations such as mountain peaks and ridges with long snow‐cover duration for breeding. Sites with high proportions of deciduous forest and abandoned pasture were avoided. Local colonization was higher at convex landscape formations and by high coniferous forest coverage and forest‐edge length. Local extinction, on the other hand, was lower at convex landscape formations and high‐elevation sites. Our results suggest that shorter persistence of snow fields caused by climate change and degradation of feeding grounds through land‐use abandonment might severely deteriorate food availability for the species, which is likely to have contributed to the observed decline. For conservation of the Alpine Ring Ouzel, we recommend adopting measures to mitigate the negative effects of climate warming and improve habitat quality. The creation of small‐scale mosaics of sparse conifer forests and regularly grazed pastures, especially on north‐ and east‐facing slopes on the lee sides of hills, mountain peaks or ridges, should be supported.