Distinguishing Stressors Acting on Land Bird Communities in an Urbanizing Environment

Abstract

Urbanization has profound influences on ecological communities, but our understanding of causal mechanisms is limited by a lack of attention to its component stressors. Published research suggests that at landscape scales, habitat loss and fragmentation are the major drivers of community change, whereas at local scales, human activity and vegetation management are the primary stressors. Little research has focused on whether urbanization stressors may supplant natural factors as dominant forces structuring communities. We used model selection to determine the relative importance of urban development, human activity, local and landscape vegetation, topography, and geographical location in explaining land bird species richness, abundance, and dominance. We analyzed the entire community and groups of species based on ecological characteristics, using data collected in remnant forests along a gradient of urban development in the Lake Tahoe basin, California and Nevada, USA. Urbanization stressors were consistently among the principal forces structuring the land bird community. Strikingly, disturbance from human activity was the most important factor for richness in many cases, surpassing even habitat loss from development. Landscape-scale factors were consistently more important than local-scale factors for abundance. In demonstrating considerable changes in land bird community structure, our results suggest that ecosystem function in urban areas may be severely compromised. Such changes compel local- and landscape-scale management, focused research, and long-term monitoring to retain biodiversity in urban areas to the extent possible.

A meta‐analysis of the effects of urbanization on ground beetle communities

“…The mechanisms underlying these trophic level differences, however, remain to be tested. Predatory beetles may be generally more sensitive to the higher levels of disturbance and habitat fragmentation of urban forests (McKinney 2002, Donnelly and Marzluff 2006, Schlesinger et al 2008. The relative sensitivity of predators, omnivores, and herbivores may also reflect differences in resource availability between rural and urban forests and may indicate that trophic processes are frequentv www.esajournals.org ly disrupted in cities (Faeth et al 2005).…”

“…We reiterate the call of multiple authors (McIntyre 2000, McDonnell and Hahs 2008, Niemelä and Kotze 2009, Magura et al 2010, Raupp et al 2010 to quantify the factors that actually vary along the urban gradient and may be most influential in determining species responses. Model selection could then be employed to identify the most important factors given the data, as has been done for spiders, bees, and birds by Sattler et al (2010), birds by Schlesinger et al (2008), and amphibians by Parris (2006). Future studies could also include carefully designed observational studies that sample from orthogonal gradients, as well as experimental manipulations of certain variables such as resource availability or local habitat structure.…”

The breeding performance of raptors in urban landscapes: a review and meta-analysis

“…Sumasgutner et al 2014a;Russo and Ancillotto 2015;Demeyrier et al 2016). For instance, increased human disturbance associated with urban areas, including pedestrian traffic, has been found to reduce nest spacing (Fernández-Juricic 2002), species density (Fernández-Juricic and Tellería 2000) and species richness (Schlesinger et al 2008). The introduction of non-native predators (Bonnington et al 2013;Loss et al 2013), collisions with buildings and vehicles (Erritzoe et al 2003;Bishop and Brogan 2013), and pollution ; Kempenaers et al 2010;Isaksson 2015) have also been shown to have negative effects on the health, survival and reproduction of urban wildlife.…”

Breeding performance of an apex predator, the peregrine falcon, across urban and rural landscapes

“…These changes represent major challenges for some wildlife populations through associated habitat loss and fragmentation (McKinney 2006), barriers to dispersal (Erritzoe et al 2003;Bishop and Brogan 2013), increased disease (Dhondt et al 2007), noise and light pollution Kempenaers et al 2010), human disturbance (Schlesinger et al 2008), increased mortality due to road traffic accidents and collisions (Erritzoe et al 2003), and high densities of domesticated predators such as cats (Felis catus) (Schlesinger et al 2008). Although many species are unable to persist in urban environments, others are able to colonise and reproduce successfully in even the most extreme urban environments (Blair 1996;Marzluff 2001).…”