Linking Socioeconomics to Biodiversity in the City: The Case of a Migrant Keystone Bird Species

Abstract

Billions of wild animals migrate every year between breeding and non-breeding sites, facing new environmental conditions due to anthropogenic change. Although cities engender profound environmental changes, they provide habitat for some migratory birds contributing to conserving biodiversity and restoring human-nature connections. A common issue in Neotropical cities is their socio-environmental segregation, that might result in wealthier people having access to greater biodiversity in their neighborhoods. Although growing evidence shows a relationship between wealth and biodiversity in cities, it remains poorly investigated in relation to animals, particularly migratory birds. We present the first study on the effects of socioeconomic status on a Neotropical austral migrant considered a keystone species. We tested whether neighborhood socioeconomic category and habitat variables relate to the occurrence of the Green-backed Firecrown hummingbird in its overwintering habitat in urban areas. We hypothesized that higher socioeconomic status of neighborhoods would positively influence hummingbird occurrence through mediating effects of woody plant cover. We found that hummingbird occurrence increased with socioeconomic level of neighborhoods and woody cover. Specifically, we found that socioeconomic level influenced hummingbird occurrence indirectly through woody and shrub cover. We also found a direct effect of socioeconomic level on hummingbird occurrence suggesting the need for further research. Our findings show that wealthier neighborhoods exhibit greater woody cover and higher hummingbird occurrence than poorer neighborhoods, providing dissimilar opportunities to experience nature close to home. In neighborhoods where people of lower socioeconomic status live, strategies aiming to increase tree and shrub cover will promote a more environmentally just city.

Opposite Responses of Native and Nonnative Birds to Socioeconomics in a Latin American City

“…We used 120 sites located in residential areas of different socioeconomic levels selected by Villaseñor and Escobar (2022) [23]. To select sites, these authors used a digital layer of the socioeconomic distribution [40].…”

“…The low socioeconomic group comprised households with less education and a mean annual household income lower than US 8400 [41]. Using the "raster" package [42] in R 4.1.2 [43], this layer was rasterized at a 200 m × 200 m cell size to generate a grid of potential sample sites [23]. Because previous research in Santiago describes a decrease in species richness towards the interior of the city [21], the city was stratified in two areas: edge (less than 5 km from the urban limit) and interior (more than 5 km from the urban limit towards the interior of the city).…”

“…Because previous research in Santiago describes a decrease in species richness towards the interior of the city [21], the city was stratified in two areas: edge (less than 5 km from the urban limit) and interior (more than 5 km from the urban limit towards the interior of the city). A stratified random selection approach was used to select 20 sites (raster cells) in residential areas for each combination of socioeconomic level (three levels: high, medium, and low) and distance to the urban boundary (two levels: edge and interior), leading to 120 sites (Figure 1; [23]).…”

“…Birds were surveyed twice at 120 sites during the austral breeding season (from 12 October to 4 November 2021) to reduce bias associated with particular conditions of a given day within the season. Two surveys per season provide a reliable indication of bird trends and have successfully described bird community response in our city [21,23,31]. At each site, the point count method was used to record all birds seen or heard during 5 min within a visually estimated 50 m radius plot [44] but excluding birds flying over that did not use the area [21].…”

“…Although an increasing number of studies are investigating the luxury effect, most research has focused on plants, with few empirical studies on fauna [22] and the factors underpinning their response [23]. Past research has shown a positive relationship among human wealth (income) and bird species richness in urban parks, residential areas [24], and municipal districts [25].…”