Theodore R. Simons

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Recognition and analysis of spatial autocorrelation has defined a new paradigm in ecology. Attention to spatial pattern can lead to insights that would have been otherwise overlooked, while ignoring space may lead to false conclusions about ecological relationships. We used Gaussian spatial autoregressive models, fit with widely available software, to(More)
—Use of point-count surveys is a popular method for collecting data on abundance and distribution of birds. However, analyses of such data often ignore potential differences in detection probability. We adapted a removal model to directly estimate detection probability during point-count surveys. The model assumes that singing frequency is a major factor(More)
Recent, worldwide amphibian declines have highlighted a need for more extensive and rigorous monitoring programs to document species occurrence and detect population change. Abundance estimation methods, such as mark–recapture, are often expensive and impractical for large-scale or long-term amphibian monitoring. We apply a new method to estimate proportion(More)
—We have developed a system for simulating the conditions of avian surveys in which birds are identifi ed by sound. The system uses a laptop computer to control a set of amplifi ed MP3 players placed at known locations around a survey point. The system can realistically simulate a known population of songbirds under a range of factors that aff ect detection(More)
We examined the relationship between songbird relative abundance and local and landscape-scale habitat variables in two predominately midto late-successional managed National Forests in the southern Appalachian Mountains, USA. We used partialregression analysis to remove correlations between habitat variables measured at different spatial scales (local(More)
—We used a bird-song simulation system to experimentally assess the effects of habitat, vegetation structure, and background noise on detection probability in aural avian point counts. We simulated bird songs of seven species in two habitats (mixed pine–hardwood forest and deciduous forest) and two leaf conditions (leaves on and leaves off) with two levels(More)
—Point-count surveys are o en used to collect data on the abundance and distribution of birds, generally as an index of relative abundance. Valid comparison of these indices assumes that the detection process is comparable over space and time. These restrictive assumptions can be eliminated by estimating detection probabilities directly. We generalize a(More)
Many factors affect the number of birds detected on point count surveys of breeding songbirds. The magnitude and importance of these factors are not well understood. We used a bird song simulation system to quantify the effects of detection distance, singing rate, species differences, and observer differences on detection probabilities of birds detected by(More)
—Studies of source–sink dynamics are oft en prompted by concerns about negative population trends. Estimates of population trajectories are usually based on assumptions about survival rates and empirical measures of fecundity. Most models ignore the infl uence of the rates of renesting and multiple brooding. We used the Ovenbird (Seiurus aurocapilla) as a(More)
Abundance and population density are fundamental pieces of information for population ecology and species conservation, but they are difficult to estimate for rare and elusive species. Mark--resight models are popular for estimating population abundance because they are less invasive and expensive than traditional mark-recapture. However, density estimation(More)