Urban noise and surrounding city morphology influence green space occupancy by native birds in a Mediterranean-type South American metropolis

Abstract

Urban green spaces provide natural habitat for birds in urban landscapes, yet the effects of noise and surrounding urban morphology on bird community structure and distribution are not well understood in Latin America, the second most urbanized region in the world. Santiago of Chile is the single city belonging to the Mediterranean ecosystem in South America and is subject to extensive urbanization as seen throughout Latin America. We examined the role of 65 urban green spaces-6 large urban parks (PAR) and 59 small green spaces (SGS)-in harboring native birds during winter 2019, analyzing the quality of green areas in terms of vegetation (i.e. NDVI, native vegetation, and tree cover), exotic bird species, noise levels, and surrounding urban morphology (i.e. building height and cover). Significantly higher noise levels were detected in SGS, along with significantly greater exotic bird (n = 4) richness and abundance than PAR, which possessed significantly greater native bird (n = 25) richness and abundance. Native birds were more abundant than exotic birds in green spaces with average noise levels < 52 dB and average NDVI > 0.5. Occupancy models indicate that green space occupancy by 50% of modeled native bird species was influenced by maximum noise levels, playing a larger role than vegetation (30%) and urban morphology (0%). We stress the importance of developing networks of large green spaces in rapidly urbanizing regions, with abundant tree cover, surrounded by smaller urban morphology, and regulating noise levels to ensure the conservation of native bird communities in cities, particularly those that are threatened.

Figure 1

Average noise levels in green spaces and average building height surrounding green spaces at which native bird species occur: a) urban avoiders, b) urban utilizers, with Sephanoides sephaniodes considered separately, and c) urban dwellers. Marginal density plots indicate the distribution of native birds at varying average noise levels in green spaces (top) and varying average building height surrounding green spaces (right). Decibel level comparisons (based on values established by Yale EHS) are displayed in the arrow at the bottom for reference.

Figure 2

Occupancy probability plots for species whose occupancy was most influenced by average maximum noise levels in green spaces in Santiago, Chile: (a) native urban avoider species, (b) native urban utilizer species, and (c) native urban dweller species. Plots are based on the models summarized in Table 2. Gray lines represent 95% confidence intervals.

Figure 3

Study area within the Metropolitan Region of central Chile. Green points represent small green spaces (SGS) and blue points are large urban parks (PAR) sampled during winter 2019. Map was created using QGIS version 2.18.23 (https://www.qgis.org) with the Google Satellite plugin for QGIS (Map data^© 2015 Google).