Abstract
There is mounting evidence that urban areas influence biodiversity. Generalizations however require that multiple urban areas on multiple continents be examined. Here we evaluated the role of urban areas on avian diversity for a South American city, allowing us to examine the effects of urban features common worldwide, using the city of Valdivia, Chile as case study. We assessed the number of birds and their relative abundance in 152 grid cells of equal size (250 m2) distributed across the city. We estimated nine independent variables: land cover diversity (DC), building density (BD), impervious surface (IS),municipal green space (MG),non-municipal green space (NG), domestic garden space (DG), distance to the periphery (DP), social welfare index (SW), and vegetation diversity (RV). Impervious surface represent 41.8% of the study area, while municipal green, non-municipal green and domestic garden represent 11.6%, 23.6% and 16% of the non- man made surface. Exotic vegetation species represent 74.6% of the total species identified across the city. We found 32 bird species, all native with the exception of House Sparrow and Rock Pigeon. The most common species were House Sparrow and Chilean Swallow. Total bird richness responds negatively to IS and MG, while native bird richness responds positively to NG and negatively to BD, IS DG and, RV. Total abundance increase in areas with higher values of DC and BD, and decrease in areas of higher values of IS, SW and VR. Native bird abundance responds positively to NG and negatively to BD, IS MG, DG and RV. Our results suggest that not all the general patterns described in previous studies, conducted mainly in the USA, Europe, and Australia, can be applied to Latin American cities, having important implications for urban planning. Conservation efforts should focus on non-municipal areas, which harbor higher bird diversity, while municipal green areas need to be improved to include elements that can enhance habitat quality for birds and other species. These findings are relevant for urban planning in where both types of green space need to be considered, especially non-municipal green areas, which includes wetlands, today critically threatened by urban development.
Highlights
Urbanization is one of the most extreme forms of habitat transformation and it is increasing at a high rate [1]
Overall we found conspicuous relationships between the components of urban form and bird richness and abundance
Our findings are similar to general patterns described for urban birds in other regions of the world; with high-resolution urban form data, we were able to detect patterns that have not been previously described
Summary
Urbanization is one of the most extreme forms of habitat transformation and it is increasing at a high rate [1]. The transformation of natural habitats into agricultural and urbanized areas results in a mosaic of land types ranging from heavily built urban centers to natural or seminatural areas [2]. These extensive modifications have profound effects on the structure and function of ecosystems and are strongly correlated with adverse impacts on avian native communities [3, 4]. Total bird abundance has been found to increase with the level of urbanization [10, 15,16,17,18,19] This response was attributed to a higher number of urban exploiter species [9, 14, 20,21,22]
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