Structural Versus Functional Habitat Connectivity Measures to Explain Bird Diversity in Fragmented Orchards

Structural Versus Functional Habitat Connectivity Measures to Explain Bird Diversity in Fragmented OrchardsHabitat connectivity plays a paramount role in the biodiversity of fragmented landscapes. Commonly, connectivity is measured using simple structural metrics, e.g. Euclidean distances between habitat patches. Recently, functional measures such as cost-distance metrics have been proposed. Cost-distance metrics account for behavioural aspects of investigated organisms. They weight the habitats of the investigated landscape according to specific cost values, and model the optimal dispersal corridor according to these values. This study investigated i) if structural or functional connectivity measures explain biodiversity in a focal habitat better and ii) if the appropriateness of the measure differs between patch and landscape scale. We mapped the landscapes within a 500 m radius around 30 fragmented traditional orchards (focal patch). Connectivity measures were based on either Euclidean distances (structural) or cost-distances (functional) to other suitable habitat patches. Birds were used as biodiversity indicators. For analysis, we calculated species richness and total abundance of all species with a preference for woody habitats. In addition, abundances of four wood-preferring bird species were also examined individually. Linear models were created using stepwise forward selection. The relative performance of structural and functional connectivity measures was scale dependent.