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1 March 2013 Distance to a Road is Associated with Reproductive Success and Physiological Stress Response in a Migratory Landbird
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We investigated the impacts of an unpaved road on the distribution, reproduction, and stress physiology of Mountain White-crowned Sparrows (Zonotrichia leucophrys oriantha) in a high-elevation subalpine ecosystem. We found and monitored 152 sparrow nests over 3 years and captured 123 sparrows over 2 years for standardized stress series experiments. Distance of a nest to the road was associated with reproductive success, and low success near the road was primarily because of high rates of nest desertion. The probability of a nest succeeding rose with increasing distance from road up to 40 m, but nests beyond 40 m experienced lower nest success, possibly because of increased predation. Nests at intermediate distance were approximately twice as likely to succeed (70% survival rate) as those near (36% survival) or far (37% survival) from the road. Stress response of male sparrows subjected to a standardized field stress protocol was elevated within 20 m of the road (38.34 ± 5.76 ng/ml) compared to those at greater distances (23.89 ± 2.01 ng/ml). Our study is the first to document the association between the distance to a road and blood corticosterone levels in any bird species. The results present strong evidence of impacts of a road on nest success of a migratory songbird. This relatively low-traffic, low-speed road clearly presents problems, even for a bird species not thought to be sensitive to disturbance.

2013 by the Wilson Ornithological Society
Matthew S. Dietz, Courtney C. Murdock, L. Michael Romero, Arpat Ozgul, and Johannes Foufopoulos "Distance to a Road is Associated with Reproductive Success and Physiological Stress Response in a Migratory Landbird," The Wilson Journal of Ornithology 125(1), 50-61, (1 March 2013).
Received: 30 March 2011; Accepted: 1 July 2012; Published: 1 March 2013

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