Citation:

Etterson, M., R. Greenberg, AND T. Hollenhorst. Landscape and regional context differentially affect nest parasitism and nest predation for Wood Thrush in central Virginia, USA. The Condor: Ornithological Applications. University of California Press at Berkeley, Berkeley, CA, 116(2):205-214, (2014).

Impact/Purpose:

This manuscript has two basic objectives. The first is to present a case study in competing risks analysis of avian nest survival data. The second is to examine the effect of landscape structure on avian nesting success in the Shenandoah Valley, Blue Ridge, and Piedmont of Central Virginia, USA. The manuscript is intended for ornithologists, land managers, and risk assessors. It provides a case study of how the topic of competing risks may help provide a more precise understanding of the impacts of anthropogenic stressors on wildlife populations that also face natural stressors.

Description:

Many empirical studies have shown that forest-breeding songbirds, and neotropical migrants in particular, are found in lower abundance in small patches of forest in the Eastern United States compared to similar, but larger patches in the same region. A common hypothesis for the cause of this pattern is that birds suffer greater rates of nest predation in smaller forest patches and in fragmented landscapes. However, reported patterns of avian response to forest loss and fragmentation vary among studies, species, and regions of the United States and may depend on landscape context within regions. To compare the performance of different types of metrics of habitat pattern resulting from deforestation, we analyze survival data for 336 nests of multiple species nesting in various sized forest fragments in central Virginia, USA. Metrics of distance to edge gained support in analyses of Wood Thrush data alone (200 nests) and in analyses of all species pooled. Metrics of habitat composition also gained support, but measures of habitat configuration received relatively little support. Patterns of nest success at the landscape scale (low, medium, and high forest cover) did not conform to patterns reported in other studies. We conclude that, while there is substantial evidence for effects of habitat- and landscape-structure on avian nest success in forests of the Eastern and Midwestern United States, these patterns do not seem to conform to a simple theoretical explanation.

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