Fragmentation effects on woodlark habitat selection depend on habitat amount and spatial scale

Abstract

AbstractHabitat loss and fragmentation are key drivers of biodiversity loss. However, they are usually confounded, making it difficult to separate fragmentation effects from those of habitat loss. In addition, it has been shown that often fragmentation negatively affects biodiversity only below a certain threshold of habitat amount. We investigated the separate and interactive effects of habitat amount and fragmentation on habitat selection of the woodlark at 10 spatial scales. In southern Switzerland this passerine mainly breeds in ground‐vegetated vineyards, which therefore represent the focal habitat type in this study. Additionally, we investigated land cover, topographic and climatic variables at the same 10 scales to obtain a holistic picture of species‐habitat associations. Habitat selection was analyzed at two hierarchical levels: home range selection within the study area and habitat use within home ranges. Home range selection was strongly driven by an interactive effect of habitat amount and fragmentation: woodlarks avoided fragmented areas if habitat amount was below 20% but exhibited a preference for fragmented areas if habitat amount exceeded this threshold. Both habitat amount and fragmentation most strongly affected habitat use at the 100 m scale. We did not find such interactive effects for habitat use within home ranges. At this level, habitat amount at a 50 m scale influenced woodlark presence positively with no significant effects of fragmentation. Furthermore, woodlarks preferred evenly sloped landscape mosaics interspersed with steppes and groves. Two main insights emerge from our study. First, these results highlight the necessity of studying scale explicit and interactive effects of habitat amount and fragmentation when addressing ecological questions, such as habitat selection in birds. Second, we provide management recommendations for farmers: more vineyards should be vegetated and arranged as disjunct patches where their surface covers more than 20% of the landscape but be aggregated where vegetated area is lower.