Avifauna and urban encroachment in time and space

Urban expansion significantly alters fringe environments often with undesirable impacts on biodiversity. Consequently, there is a need to define clear conservation objectives for areas subject to urban encroachment. Urban fringe development is a highly dynamic process, both spatially and temporally, but few studies are equipped to examine its temporal effects on biota. We aimed to explore the impacts of urban encroachment on avifauna through space and time. We used records from an extensive 14-year monitoring program undertaken in temperate woodland. We fitted hierarchical generalised linear models to assess individual species responses to the distance from monitoring sites to the urban boundary, and the temporal rate of change in this distance through time. We used factorial analysis on mixed data to examine trait group responses to these predictors. Our results indicated that the occurrence of approximately half of the study region’s avifauna is strongly linked to the proximity of their habitat to the urban fringe, but that the impact of urban fringe development on the occurrence of some species changed through time. We identified several species of conservation concern that respond negatively to large annual increases in urban fringe development, irrespective of its proximity to suitable habitat. Species responses to urban proximity were linked to life history traits, with small, migratory, woodland-dependent species that rely on midand upper-canopy structures, clearly disadvantaged by urban environments. Our findings demonstrate the breadth of species responses to urban encroachment over much larger distances than is typically investigated in urban ecological studies. We identify guilds vulnerable to the impacts of urban fringe development, and therefore in need of ecologically sensitive urban design. We argue that future urban expansion toward important fringe habitats will need to be planned strategically through space and time.