Additionally, proximity to off-trail vehicles such as snowmobiles has been associated with elevated levels of stress hormones in the gray wolf ( Canis lupus) and the elk ( Cervus canadensis) ( Creel et al., 2002). Proximity to roads increases physiological stress in birds including the northern spotted owl ( Strix occidentalis caurina) and the mountain white-crowned sparrow ( Zonotrichia leucophrys oriantha) ( Crino et al., 2011 Hayward and Wasser, 2006 Wasser et al., 1997). Benítez-López et al., 2010 Fahrig and Rytwinski, 2009 Holderegger and Di Giulio, 2010). For example, areas near roads are associated with decreased population density, genetic diversity and biodiversity in many taxa including plants, mammals, reptiles, amphibians and birds (e.g.
Although roads have many positive effects for people, they can engender negative effects for biological communities. Roads are a ubiquitous component of human-altered landscapes. edge effects, pollution and mechanical vibration) may be more important than traffic noise in explaining elevated nestling stress responses in this species. Therefore, when evaluating the mechanisms through which roads affect avian populations, other factors (e.g. These results indicate that traffic noise does affect physiology and development in white-crowned sparrows, but not at all as predicted. Surprisingly, nestlings exposed to traffic noise had lower glucocorticoid levels and improved condition relative to control nests. Based on prior studies, we expected the traffic noise treatment to result in elevated stress hormones (glucocorticoids), and declines in immune function, body size, condition and survival. Following exposure to traffic noise we measured nestling stress physiology, immune function, body size, condition and survival. We exposed nestling mountain white-crowned sparrows ( Zonotrichia leucophrys oriantha) to experimentally elevated traffic noise for 5 days during the nestling period. Here, we examine one mechanism through which roads could affect birds: traffic noise. Although the consequences of roads on individuals and communities have been well described, the mechanisms through which roads affect birds remain largely unexplored. In birds, roads decrease reproductive success and biodiversity and increase physiological stress. Roads have been associated with behavioral and physiological changes in wildlife.
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