Characterizing avian survival along a rural‐to‐urban land use gradient

Abstract

Many avian species persist in human-dominated landscapes; however, little is known about the demographic consequences of urbanization in these populations. Given that urban habitats introduce novel benefits (e.g., anthropogenic resources) and pressures (e.g., mortality risks), conflicting mechanisms have been hypothesized to drive the dynamics of urban bird populations. Top-down processes such as predation predict reduced survivorship in suburban and urban habitats, whereas bottom-up processes, such as increased resource availability, predict peak survival in suburban habitats. In this study, we use mark-recapture data of seven focal species encountered between 2000 and 2012 to test hypotheses about the processes that regulate avian survival along an urbanization gradient in greater Washington, D.C., USA. American Robin, Gray Catbird, Northern Cardinal, and Song Sparrow exhibited peak survival at intermediate and upper portions of the rural-to-urban gradient; this pattern supports the hypothesis that bottom-up processes (e.g., resource availability) can drive patterns of avian survival in some species. In contrast, Carolina Chickadee showed no response and Carolina and House Wren showed a slightly negative response to urban land cover. These contrasting results underscore the need for comparative studies documenting the mechanisms that drive demography and how those factors differentially affect urban adapted and urban avoiding species.

Differences in measures of boldness even when underlying behavioral syndromes are present in two populations of the song sparrow (Melospiza melodia)

“…Scales et al (2013) reported that aggressive birds appeared able to gain high-quality territories, which also suggests benefits to high levels of aggression. Grunst et al (2014) found that urban song sparrows had lower levels of cortisol and better feather quality than rural birds, and Evans et al (2015) found that song sparrow survivorship is higher in more urbanized parts of an urban-rural gradient. While these studies do not mean that urban habitats are preferable, they do suggest that urban habitats are not suboptimal for song sparrows.…”

Dispersal in the Urban Matrix: Assessing the Influence of Landscape Permeability on the Settlement Patterns of Breeding Songbirds

“…Proportional canopy cover and impervious surface (30 m resolution, Xian et al, 2011) were used as proxy variables in constructing habitat suitability models. While we acknowledge that these variables do not represent the totality of habitat variation along the rural-to-urban gradient, these land cover metrics have been shown to be predictive of avian nest success (canopy cover and impervious surface, Ryder et al, 2010), adult survival (impervious surface, Evans et al, 2015), and community composition (impervious surface, Evans, 2015). All spatial analyses were carried out in R using packages raster (Hijmans, 2015) and sp (Pebesma and Bivand, 2005).…”

The Influence of Urban Environments on Oxidative Stress Balance: A Case Study on the House Sparrow in the Iberian Peninsula

“…However, these novel and potentially stressful conditions generated by urban environment processes have also provided new opportunities for certain species to gain an ecological advantage by exploiting city resources (Lepczyck and Warren, 2012;Costantini et al, 2014). Such resources are characterized by lower predation rates (Evans et al, 2015), higher environmental temperatures (Tryjanowski et al, 2015), lower competition for resources (Kark et al, 2007), and a constant, abundant, and more predictable food resources supply, in comparison with the surrounding non-anthropogenic areas (Shochat, 2004;Oro et al, 2013;Andersson et al, 2015;Tryjanowski et al, 2015;Marzluff, 2016).…”