Scalar effects of vegetation on bird communities in an urbanizing desert ecosystem

Abstract

We analyzed how urbanization in a desert ecosystem affects avian distribution at two distinct scales. At the regional level, we compared how urban land use configuration, relative to its surrounding agricultural fields and desert, affected the distribution of native and exotic species. While exotic species are isolated to the city; native species actively utilize the entire region, even occurring at higher densities in the city than in some areas of the desert. We also used this approach to compare four foraging guilds of birds: granivores, nectivores, omnivores, and insectivores. Granivores occurred mostly in agricultural fields and in the surrounding urban areas. Nectivores and omnivores occurred throughout the region, but mostly within the city. In contrast, insectivores occurred mostly in the desert. At a more local scale, we tested how the abundance of native species, exotics species and the foraging guilds of birds responded to vegetation cover measured at varying spatial scales (0.1 km-10 km). Bird guilds responded to vegetation at different scales, depending on the association between their life history and vegetation. Granivore abundance was most strongly correlated with vegetation at relatively fine spatial scales, followed by nectivores and omnivores at larger scales; whereas insectivores did not correlate with vegetation at any scale. Exotic and native species showed strikingly opposite trends in their association with vegetation. Native species showed the best fit at the smallest spatial scale and became insignificant at larger scales, whereas the highest correlation of exotic species with vegetation was at moderate to larger scales. While guild relationship with vegetation appears straightforward, the differences between exotic and native birds may indicate a complex response to environmental factors. Possibly, native species are more sensitive than exotics on vegetation abundance for food and shelter, which in the desert is highly variable Urban Ecosyst (2010) 13:155-167 depending on water availability. In contrast, exotic species, tightly connected to the urban infrastructure, likely respond to the enhanced and homogenized resource abundance characteristic of desert cities. Our results suggest that relationships between birds and vegetation may bear important information that can be revealed when considering smaller class levels than total species diversity.

The Good, the Bad, and the Ugly of Urbanization: Response of a Bird Community in the Neotropical Andes

“…In the case of omnivorous birds, we found an "U" shape response with a decrease in abundance in the first levels of urbanization, but another increase of abundance in more urbanized areas. These results differ from some studies that reported that abundance and species richness were lower in the least urbanized areas (Walker and Shochat, 2010;Huang et al, 2015). The shift in this pattern could be a consequence of the appearance of exotic generalist bird species, associated with the consumption of food provided directly or indirectly by humans.…”

“…While bird community response has been consistent across different regions, these effects are expected to be species dependent, with certain species being favored by new habitats and resources, and others being harmed by habitat-level alterations (Chace and Walsh, 2006;Walker and Shochat, 2010;Valente-Neto et al, 2021). Our results showed trophic guild-dependent responses.…”

Disentangling the drivers of urban bird diversity in the non‐breeding season: A general synthesis

“…This coincides, in part, due to species able to use feeding sites are abundant during winter in Finnish cities (Jokimäki & Suhonen, 1998). Nonetheless, this finding contrasts as those expected, as it is often stated that urbanisation favours omnivorous birds (Walker & Shochat, 2010). This was also contrary to our expectation, since it has been previously reported that the tree canopy is a preferred feeding stratum for wintering birds inhabiting cities (Amaya-Espinel & Hostetler, 2019).…”

Respuestas de la comunidad de aves a las variables del hábitat local y del paisaje en la ciudad de Santiago de Chile

“…Al contrario, las aves granívoras presentarían mayor tolerancia a la urbanización, e incluso pueden ser favorecidas por cambios antrópicos (Chace and Walsh 2006;Perepelizin and Faggi 2009). En áreas urbanas, las aves generalistas con una dieta omnívora parecen incrementar su abundancia (Clergeau et al 1998;Lim and Sodhi 2004;Walker and Shochat 2010).…”

“…Solo el gremio de aves omnívoras se asoció positivamente con ambientes más construidos. Este resultado coincide con el patrón reportado en la literatura, en el que los omnívoros, debido a sus dietas generalistas, tienden a aumentar con el nivel de construcción (Chace and Walsh 2006;Walker and Shochat 2010;Amaya-Espinel et al 2019).…”