Geology topics
Thomas R. Stanley
Publications and source records attributed to Thomas R. Stanley.
Breeding habitat use by sympatric and allopatric populations of Wilson's Warblers and Yellow Warblers
We studied Wilson's Warbler ( Wilsonia pusilla ) and Yellow Warbler ( Dendroica petechia ) habitat use in allopatric and sympatric populations in the Rocky Mountains of northern Colorado and southeastern Wyoming in order to better understand the different habitat needs and interactions of these two species. Foraging Wilson's Warblers and Yellow Warblers used very similar habitat, both selecting larger, more open shrubs. In spite of similar foraging habitat, comparisons of habitat use by the two species at the sympatric sites yielded no evidence of foraging habitat partitioning or exclusion. There was evidence of nesting habitat partitioning. Wilson's Warblers nested on the ground, with some evidence that they used smaller, more densely stemmed shrubs under which to nest. Yellow Warblers are shrub nesters and selected larger, more open shrubs in which to nest. Results provide no evidence that Yellow Warblers can be blamed for population declines in Wilson's Warblers.
Estimator selection for closed-population capture: recapture
For valid statistical inference, it is important to select an appropriate statistical model. In the analysis of capture-recapture data under the closed-population models of Otis et al. (1978), information theoretic and hypothesis testing approaches to model selection are not practical, because some of the models have likelihoods with nonidenti- fiable parameters. A further problem is that, for some of the Otis et al. models, multiple estimators exist but there is no objective basis for deciding which estimator to use for a particular dataset. In CAPTURE, a computer program for estimating parameters un- der the closed models of Otis et al., a linear discriminant classifier is used to select an appropriate model. This classifier frequently selects the incorrect generating model in simulation studies, and it provides no guidance on which estimator to use once a model has been selected. In this study, we develop new classifiers for selecting the best esti- mator (as opposed to the generating model) and evaluate their performance. In addition, we investigate an estimator averaging approach to estimation that is a modification of the model averaging approach described by Buckland et al. (1997). We found that, in general, the overall performance of the new classifiers was unimpressive. In contrast, the estimator averaging approach we investigated performed well.
Effects of roadside habitat and fox density on a snow track survey for foxes in Ohio
Many methods have been used to survey red fox (Vulpes vulpes) and gray fox (Urocyon dnereoargenteus) populations. However, none has proven entirely satisfactory, and wild foxes remain one of the most difficult economically important wildlife species to monitor. In this study we evaluated the reliability of a snow track survey method for foxes by investigating whether the average number of road crossings per fox is influenced by changes in roadside habitat or changes in fox density. Several snow track surveys were conducted in two Ohio counties during January and February, 1984. Data on roadside habitat, relative fox densities, and fox crossings were collected. Results suggested that changes in roadside habitat could influence the average number of crossings per fox and, therefore, changes in the index could occur independent of actual population changes. We found no evidence that crossings per fox varied with fox density, but further research is needed to substantiate this finding.