Landscape heterogeneity and management practices drive habitat preferences of wintering and breeding birds in intensively-managed fruit-tree plantations

Intensively-managed fruit-tree plantations consisting of low-stem trees have progressively replaced traditional high- and mid-stem orchards in Europe during the intensification of agriculture in the second part of the 20th century. Such perennial agricultural systems often form dense, homogeneous landscapes interspersed with open fields, urban areas and semi-natural structures. This observational study investigated the patterns driving landscape- and field-scale habitat preferences of bird communities in landscape units with varying fractions of intensively-managed fruit-tree plantations. At landscape scale, habitat homogeneity, notably a large proportion of fruit-tree plantations, had negative effects on both overall bird species richness and on the abundance of insectivorous birds. A higher proportion of semi-natural features, such as natural woody structures (hedgerows, isolated trees and forest patches) and marshes, positively affected overall bird species richness and abundance as well as insectivorous bird abundance. At field scale, we detected general, trait- and species-specific preferences for older trees during both winter and spring. In winter, leftover fruit is a crucial resource driving field selection by the avifauna. In spring, bird preferences for low and sparse ground vegetation were best explained by increased food accessibility for terrestrially foraging birds. Overall landscape heterogeneity as well as in situ management practices both matter to enhance bird habitat in fruit-tree plantations. Increasing the proportion of diverse semi-natural structures would promote wintering and breeding bird diversity and abundance. At field scale, conditions for birds can be improved by preserving older fruit-tree plantations and by maintaining patches of bare ground and short vegetation in the plantation inter-tree rows. However, given the current high-intensity management in most fruit-tree plantations in our study area, promoting natural features within the wider landscape matrix might represent a more cost-effective solution to enhance bird biodiversity in this agro-ecosystem.