A functional trait approach reveals the effects of landscape context on ecosystem services provided by urban birds

Abstract

Land use intensification in urban areas can have profound effects on biological communities that provide valuable ecosystem services to urban residents. We used a functional response and effect trait approach to determine how bird species' responses to local and landscape-scale habitat of urban green spaces affects the supply of cultural and regulating ecosystem services. We sampled bird communities and habitat variables in urban green spaces that varied in local and landscape-scale habitat composition and compiled a dataset of species' response and effect traits related to nesting, foraging, diet, and visual and acoustic aesthetic appeal. Overall, the landscape-scale context of a green space had a stronger influence on species' abundances than local-scale habitat. Landscape-scale impervious surface surrounding our study sites interacted with response traits related to nesting in human-built structures, clutch size, and consumption of invertebrates to drive bird species' abundances. Because correlations between response and effect traits can influence the effect traits available to provide ecosystem services at a site, we explored the correlation of these three response traits to a suite of effect traits and found the response traits were correlated with several effect traits related to diet and regulating services but correlated with few of the plumage and acoustic traits that produce cultural services. Finally, we found that effect traits associated with cultural and regulating ecosystem services varied strongly along the landscape-scale gradient of urbanization. Sites with high impervious surface cover are expected to have low levels of invertebrate pest control and visual appeal but high levels of acoustic appeal, diet evenness (generalism), and granivory. Overall, our study highlights the key role of landscape-scale habitat in driving bird-mediated ecosystem services and underscores the importance of regional urban planning to create healthy and livable cities.