Thesis

Residential irrigation as a driver of urban bird community structure

The availability of water is arguably the most important landscape factor, particularly in arid climates. Homeowner decisions regarding irrigation are likely to have a direct effect on bird species richness. Previous research has suggested a link between socioeconomics and urban species diversity. This empirical study examines a potential pathway for this relationship: Neighborhood socioeconomic status influences residential irrigation intensity, which influences plant cover, in turn influencing bird diversity. This study uses results from the Fresno Bird Count, a citizen science project, along with socioeconomic, vegetative, and irrigation data. Both bird species richness and foraging guild richness were examined. Irrigation intensity decreases in areas with greater poverty levels (P<0.0283). A multivariate model links avian species richness with poverty levels, irrigation intensity, and amount of vegetation (Whole model R2=0.682, P<0.0008). Guild richness decreases in areas of greater poverty levels (R2=0.216, P<0.0042) and less intense irrigation (R2=0.131, P<0.0303). In a multivariate model irrigation intensity, vegetative factors and poverty levels are strong predictors of guild richness (Whole model R2=0.521, P<0.0009). In arid urban areas, irrigation is a key driver of bird communities. Many communities like Fresno, CA are undergoing changes in water policies that are likely to change residents� irrigation behavior. Thus, understanding water management is critical for a deeper theoretical understanding of urban ecosystems and for effective urban policy.

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