Resistance-Based Spatial Connectivity for Migratory Raptors: A Case Study from Marmara Ereğlisi, Turkey

Abstract

Understanding how migratory raptors navigate through increasingly fragmented landscapes is essential for sustaining ecological connectivity at regional scales. This study models potential flyways for soaring migrants along the Marmara Ereğlisi coast, a critical segment of the East Europe–West Asia migratory corridor in northwestern Türkiye. A resistance-based least-cost path (LCP) framework was implemented using six spatial variables representing both anthropogenic pressures and natural facilitative structures: artificial light at night (VIIRS 2023), road proximity (OpenStreetMap), land-cover permeability (CORINE 2018), slope (Copernicus DEM), hydrological guidance (coastlines and rivers), and urban green areas (CORINE 142, OSM). All layers were normalized to a 30 m grid, weighted via literature-informed multi-criteria evaluation (WLC), and integrated into a composite resistance surface. The results reveal three primary low-cost migration corridors running parallel to the Marmara coastline, converging near coastal lagoons and agricultural mosaics while avoiding high-luminance and high-road-density zones. Overlay analysis demonstrated that approximately 72% of the modeled least-cost paths coincide with low-slope and hydrologically guided terrain, confirming the facilitative role of topography and water networks in raptor movement. Conversely, areas of intense light pollution and urban expansion were identified as major connectivity barriers. From an applied perspective, the findings highlight priority zones where urban green-infrastructure enhancement—particularly riparian restoration, vegetation buffers, and light mitigation—could reinforce both avian migratory pathways and local ecological networks. The methodology provides a replicable spatial framework for integrating migratory connectivity into urban and regional planning.