A globally declining endemic under pressure: effects of habitat and climate change on Citril Finches in the Bavarian Alps

Abstract The ongoing global biodiversity loss is a major challenge of our time. It affects all groups of organisms, but is particularly well documented in birds. The Citril Finch Carduelis citrinella , one of the few bird species endemic to Europe, is one example currently suffering from substantial population declines. We here set out to document its population development over the past 14 years (records in 2011 and 2025) in a part of the Bavarian Alps and to identify the environmental factors being crucial for the occurrence of the species. In our study area around Garmisch-Partenkirchen, the Citril Finch has declined by about 48% between 2011 and 2025. Currently occupied territories, as compared to former territories or control sites, were characterised by a richer supply of flowers, particularly of the Asteraceae family, higher numbers of solitary trees, and a concentration on south-facing slopes. Moreover, areas with stable rather than declining populations showed a shorter distance to the nearest water source, a higher proportion of Mountain Pine, and a longer distance to forest edges. These findings indicate negative impacts of reduced grazing intensity and climate change (drought periods). Our results highlight that preserving the Citril Finch’s alpine habitats depends strongly on traditional, low-intensity farming and appropriate pasture care to maintain the necessary flower-rich, open to semi-open habitats with solitary trees. Providing supplementary water sources would help to counteract the increasing water shortage caused by climate change. Given the documented population decline, targeted conservation measures in the Bavarian Alps, the species’ stronghold in Germany, are urgently needed.