Multi?Scale Spatial Effects Determine Nest Success in Small Urban Forest Patches

Abstract

Urban development and resulting habitat fragmentation affect species populations and inter-specific relationships. While urban ecology research often focuses on species distribution and abundance in habitat fragments, less is known about how urban environments affect reproductive success. Here, we show that factors driving songbird nest success in small urban forest patches vary with landscape-specific edge effects and Light Detection and Ranging (LiDAR) derived vegetation structure. Nest success declined within 30 meters of patch edge, but only in more developed urban landscapes. In addition, nest success increased along two fundamental axes of vegetation structure in urban fragments: overstory density and number of ground-to-canopy gaps. Hence, results indicate that forest fragmentation can generate sufficient variation in ecological conditions to create heterogeneity in edge effects and vegetation structure even across the limited urban development gradient. These findings expand to our understanding of fragmentation effects beyond the traditional rural-developed paradigm.