Greenspaces as shelters for the conservation of bird diversity in a big city

Abstract

Increasing in human population causes expansion of urban areas, which threatens forest lands and the biodiversity they harbor. Greenspaces act a critical role maintaining bird diversity within urban areas. Here, we evaluated the effect of spatial characteristics of urban greenspaces on bird species richness to identify the role of greenspace design on bird diversity in Mexico City’s Metropolitan Area. We collected data on bird species richness residing in 44 greenspaces and quantified abiotic, biotic and dispersal attributes of each site. These attributes include size, degree of urbanization within and around the greenspace, vegetation cover, distance between sampled greenspaces, distance to nearby greenspace, distance to the closest natural vegetation patch, distance to city center and distance to periphery of the city. We used Generalized Linear Models to determine the effect of spatial characteristics of urban greenspaces on bird species richness. We then built matrices of beta diversity between greenspaces and assessed bird taxonomic dissimilarity via multivariate Bray-Curtis cluster analysis. Our results showed that bird species richness varies between greenspaces. However, species richness was not correlated with spatial characteristics or biotic attributes (P > 0.05), and we only found marginal correlations between built cover within the greenspace and richness of resident species (P = 0.065) and waterbird species (P = 0.070). Taxonomic similarity between greenspaces was correlated with distance between sampled greenspaces (P < 0.05), however, some dispersal attributes showed no significant effect, such as distance to periphery of the city and distance to the closest natural vegetation patch. Our resultssuggest that distances from areas with greater natural vegetation cover to the innermost parts of the city were too short to function as constraints on the ability of birds to disperse to and colonize urban greenspaces. Our study provides further support for the importance of greenspaces as refuges for conservation of bird diversity in urban areas and shows how urban greenspaces are being used by different bird species within a constantly growing urban landscape.