Breeding habitat selection of declining grassland birds in the Italian Alps: A fine-scale study on Lanius collurio and insights into four co-occurring species

Grassland birds are experiencing steep and widespread declines across Europe. Mountain grasslands, despite representing some of the biodiversity-richest habitats and historically acting as refuges for many species, are increasingly threatened by abandonment, conversion to other land uses and management intensification, with severe consequences for their ecological integrity. Using a fine-scale (1-ha) approach, we assessed the landscape, topography and management-related factors driving breeding habitat selection in the red-backed shrike (Lanius collurio) and conducted exploratory analyses (because of lower sample size due to regional rarity) on habitat associations in four other declining grassland birds in the Italian Alps: yellowhammer (Emberiza citrinella), whinchat (Saxicola rubetra), skylark (Alauda arvensis), and barred warbler (Curruca nisoria). The number of breeding territories detected was generally scarce (red-backed shrike: 180, yellowhammer: 21, skylark: 11, barred warbler: four, whinchat: only two), confirming the alarming decline of these species in mountain grasslands. Habitat characteristics and landscape structural elements contributed to territory selection of breeding grassland birds. Isolated shrubs, shrublands, hedgerows, trees and tree lines promoted occurrence of red-backed shrikes, which also preferred moderately sloping areas and grasslands with higher NDVI diversity during the main chick-rearing period (July), but avoided grasslands with higher cover of woodlands and anthropogenic settlements in the surroundings. Independently of the dairy production system (maize-based, hay-based or a mix of both), pastures supported a higher density of breeding territories compared to meadows. At the same 1-ha spatial resolution, the multi-response explorative analyses revealed similar patterns for all the five focal species. Hedgerows tended to benefit all species, except for the skylark. Yellohammer appeared to prefer sites with increasing woodland cover up to approximately 5000 m2 per hectare. Many species were positively associated with mosaic habitats: red-backed shrike, barred warbler and whinchat with a combination of hedgerows and continuous shrub patches, and yellowhammer with areas combining extensive shrub cover and woodland edges. Skylark was only found in pastures at high elevations; whinchat and yellowhammer were mostly found around 1500 m a.s.l. Our findings underscore the role of structurally diverse, extensively managed grasslands as refuges for multiple co-occurring species of high conservation concern, and highlight the urgent need to integrate species-specific habitat requirements into agri-environmental policies (e.g., CAP subsidies) and landscape planning to halt ongoing biodiversity loss in mountain agroecosystems.