Townsend, TN, United States
Townsend, TN, United States

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Newell F.L.,Ohio State University | Sheehan J.,West Virginia University | Wood P.B.,U.S. Geological Survey | Rodewald A.D.,Ohio State University | And 18 more authors.
Journal of Field Ornithology | Year: 2013

Point counts are commonly used to assess changes in bird abundance, including analytical approaches such as distance sampling that estimate density. Point-count methods have come under increasing scrutiny because effects of detection probability and field error are difficult to quantify. For seven forest songbirds, we compared fixed-radii counts (50 m and 100 m) and density estimates obtained from distance sampling to known numbers of birds determined by territory mapping. We applied point-count analytic approaches to a typical forest management question and compared results to those obtained by territory mapping. We used a before-after control impact (BACI) analysis with a data set collected across seven study areas in the central Appalachians from 2006 to 2010. Using a 50-m fixed radius, variance in error was at least 1.5 times that of the other methods, whereas a 100-m fixed radius underestimated actual density by >3 territories per 10 ha for the most abundant species. Distance sampling improved accuracy and precision compared to fixed-radius counts, although estimates were affected by birds counted outside 10-ha units. In the BACI analysis, territory mapping detected an overall treatment effect for five of the seven species, and effects were generally consistent each year. In contrast, all point-count methods failed to detect two treatment effects due to variance and error in annual estimates. Overall, our results highlight the need for adequate sample sizes to reduce variance, and skilled observers to reduce the level of error in point-count data. Ultimately, the advantages and disadvantages of different survey methods should be considered in the context of overall study design and objectives, allowing for trade-offs among effort, accuracy, and power to detect treatment effects. © 2013 The Authors. © 2013 Association of Field Ornithologists.

Newell F.L.,Ohio State University | Beachy T.-A.,Ohio State University | Beachy T.-A.,Great Smoky Mountains Institute at Tremont | Rodewald A.D.,Ohio State University | And 5 more authors.
Journal of Field Ornithology | Year: 2014

Birds require additional resources for raising young, and the breeding currency hypothesis predicts that insectivorous species exploit large soft-bodied prey during the breeding season, but shift to small, likely hard-bodied, prey during the non-breeding season. To test this hypothesis, we examined prey use by Cerulean Warblers (Setophaga cerulea), foliage-gleaning Nearctic-Neotropical migrants, during the breeding and non-breeding seasons. We collected data on foraging behavior during the breeding season (including observations of prey items fed to young) in upland mixed-oak forest in southeastern Ohio in 2009 and 2010 and, during the non-breeding season, in shade coffee in the Cordillera de Merida, Venezuela, in 2008-2009. Cerulean Warblers captured 7% more large prey (visible prey extending beyond the bill) during the breeding than the non-breeding season, but foraged at similar rates during both seasons. Large, soft-bodied prey appeared to be especially important for feeding young. We found that adults delivered large prey on >50% of provisioning visits to nests and 69% of identifiable large prey fed to nestlings were greenish larvae (likely Lepidoptera or caterpillars) that camouflage against leaves where they would tend to be captured by foliage-gleaning birds. Availability of specific taxa appeared to influence tree species foraging preferences. As reported by other researchers, we found that Cerulean Warblers selected trees in the genus Carya for foraging and our examination of caterpillar counts from the central Appalachian Mountains (Butler and Strazanac ) showed that caterpillars with greenish coloration, especially Baileya larvae, may be almost twice as abundant on Carya than Quercus. Our results provide evidence for the breeding currency hypothesis, and highlight the importance of caterpillars to a foliage-gleaning migrant warbler of conservation concern. © 2014 Association of Field Ornithologists.

Sutton W.B.,University of Tennessee at Knoxville | Sutton W.B.,Tennessee State University | Gray M.J.,University of Tennessee at Knoxville | Hoverman J.T.,Purdue University | And 5 more authors.
EcoHealth | Year: 2014

Emerging pathogens are a potential contributor to global amphibian declines. Ranaviruses, which infect ectothermic vertebrates and are common in aquatic environments, have been implicated in die-offs of at least 72 amphibian species worldwide. Most studies on the subject have focused on pool-breeding amphibians, and infection trends in other amphibian species assemblages have been understudied. Our primary study objective was to evaluate hypotheses explaining ranavirus prevalence within a lungless salamander assemblage (Family Plethodontidae) in the Great Smoky Mountains National Park, USA. We sampled 566 total plethodontid salamanders representing 14 species at five sites over a 6-year period (2007–2012). We identified ranavirus-positive individuals in 11 of the 14 (78.6%) sampled species, with salamanders in the genus Desmognathus having greatest infection prevalence. Overall, we found the greatest support for site elevation and sampling year determining infection prevalence. We detected the greatest number of infections in 2007 with 82.5% of sampled individuals testing positive for ranavirus, which we attribute to record drought during this year. Infection prevalence remained relatively high in low-elevation sites in 2008 and 2009. Neither body condition nor aquatic dependence was a significant predictor of ranavirus prevalence. Overall, our results indicate that life history differences among species play a minor role determining ranavirus prevalence compared to the larger effects of site elevation and yearly fluctuations (likely due to environmental stressors) during sampling years. © 2014 International Association for Ecology and Health

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