Can aggregated patterns of urban woody vegetation cover promote greater species diversity, richness and abundance of native birds?

Rapid urban growth poses the global challenge of mitigating urbanization impacts on biodiversity. The amount and spatial arrangement of vegetation could help managers and urban planners improve habitat conditions for fauna; however, whether aggregated patterns of trees and shrubs promote greater diversity of wildlife in urban areas remains poorly understood. To provide empirical evidence to help planning and management of urban vegetation for native fauna, we evaluated the influence of amount and spatial arrangement of woody vegetation cover on species diversity, richness and abundance of native birds in a growing city located in a biodiversity hotspot. We first mapped woody vegetation cover at a high spatial resolution using satellite images (WorldView2, 0.45 m resolution) in the city of Santiago, Chile. Then, we performed a stratified random sampling approach to select 118 urban landscapes (1 km2 size) with different amounts and aggregation of woody cover. All selected urban landscapes were surveyed for birds during reproductive and non-reproductive seasons. We found the amount of woody cover positively influenced native birds, including different diet guilds. Species diversity, richness and abundance of all native, insectivorous and omnivorous birds, and the abundance of granivorous birds increased with the amount of woody cover in the urban landscape. Contrary to our hypothesis, spatial aggregation of woody cover exhibited mainly no-effect or negative effects on native birds. Our findings demonstrate prevailing positive effects of the amount of woody cover on native birds, and mostly no benefit of aggregation at 1 km2 scale. Therefore, both scattered and aggregated trees and shrubs contributed to support native birds in the city. Targeting high levels of woody cover, planting and preserving trees and shrubs (regardless of whether they aggregate or scatter across the urban landscape), will promote greater native bird diversity, mitigate negative impacts of urbanization on local birds, and help restore people-nature interactions in cities.