Developments and Applications of a Closed Capture-Recapture Robust Design Model to Avian Point Count Data.

Abstract

Here we review various methods of estimating detection probabilities for avian point counts; distance sampling, multiple observer methods, and recently proposed time-of-detection methods. We provide a general model of detection where the total probability of detection is made up of the probability of a bird singing (availability) and the probability of detecting a bird, conditional on its having sung. This approach is shown to be a special case of Pollock's robust capture-recapture design where the probability that a bird does not sing is equivalent to the probability that an animal is a temporary emigrant. We show that the time-of-detection method provides an estimate combining both probabilities and by combining the time-of-detection method with a multiple observer method it is possible to estimate the two components of the detection process separately. These results are presented in Chapter 1.

Chapter 2 presents the detailed model evaluation with model extensions and simulation studies. We report on the combined multiple-observer and time-of-detection method for estimation of the components of aural detection probabilities and population size through simulation. We focus on the dependent multiple-observer versus independent multiple-observer aspect of our combined method and evaluate which is the more effective in practice. We also evaluate the combined multiple-observer and time-of-detection method where the model assumptions may be violated.

Finally, Chapter 3 presents the development of several modeling approaches allowing for competing detection cues in estimation of population size and components of the competing cues, aural and visual, and then study these models through simulation. We also investigate advantages and disadvantages of the competing cue modeling versus the more conventional pooled cue modeling with evaluation through simulation. After the detailed explanations of our research methods and our simulated and real data results, we focus on the implications and importance of our work to field ornithologists designing point count studies and suggest possibilities for future research.