Urbanization restructures landscapes via habitat loss, fragmentation, higher ambient temperatures, increased light pollution, and predation, all of which adversely affect composition of flora and fauna. This suggests that environmental filtering, habitat selection, and dispersal may affect urban community structure. Avian community composition has been frequently examined as an ecological response to urban gradients at local scales. Local community structure may be influenced by a variety of mechanisms including environmental filtering, spatial processes, or stochastic processes. However, few studies have used the metacommunity paradigm to investigate avian community composition. Metacommunity theory differentiates factors that influence community structure at local and regional scales, and can provide insights into species turnover from rural to urban settings and traits that are related to environmental filtering. Our goal was to examine how different aspects of avian community structure are related to environmental and spatial factors.
We measured the influence of spatial and environmental variables on taxonomic composition, Shannon-Weiner diversity, species richness, species evenness. We also estimated functional diversity of diets, foraging strategies, nesting locations and morphology with Rao’s quadratic entropies for each community. Furthermore, we measured the relationship between species traits and environmental variables with an RLQ analysis.
Results/Conclusions
Environmental (F = 4.7, P = 0.001) and spatial processes (F= 4.0, P = 0.001) significantly influenced taxonomic structure. For taxonomic diversity, richness, and functional diversity, environmental variables accounted for a significant amount of variation (F = 6.0, P = 0.001), while spatial factors accounted for a nonsignificant amount of variation. Taxonomic diversity, richness and morphological diversity increased with urbanization, while evenness increased with the amount of pasture. Environmental variables were significantly related to trait characteristics (F = 5.39, P < 0.001). Invasive and frugivorous birds that nest on buildings were highly associated with urbanization. Native species that nest in shrubs or are parasitic nesters were negatively associated with urbanization. Regional and local factors played an important role on taxonomic structure. However, local factors such as urbanization, influenced aspects of species composition and trait diversity. This study highlights the importance of studying multiple aspects of diversity, especially when it comes to studying the effects urbanization has on avian community structure.