Separating Components of the Detection Process With Combined Methods: An Example With Northern Bobwhite |
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Authors: | JASON D RIDDLE STEPHEN J STANISLAV KENNETH H POLLOCK CHRISTOPHER E MOORMAN FERN S PERKINS |
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Institution: | 1. Department of Statistics, North Carolina State University, Raleigh, NC 27695-8203, USA;2. Department of Biology, North Carolina State University, Campus Box 7617, Raleigh, NC 27695-7617, USA;3. Fisheries and Wildlife Sciences Program, Department of Forestry and Environmental Resources, North Carolina State University, Raleigh, NC 27695-7646, USA;4. Department of Biology, Appalachian State University, P.O. Box 32027, 572 Rivers Street, Boone, NC 28608-2027, USA |
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Abstract: | Abstract: There are various methods of estimating detection probabilities for avian point counts. Distance and multiple-observer methods require the sometimes unlikely assumption that all birds in the population are available (i.e., sing or are visible) during a count, but the time-of-detection method allows for the possibility that some birds are unavailable during the count. We combined the dependent double-observer method with the time-of-detection method and obtained field-based estimates of the components of detection probability for northern bobwhite (Colinus virginianus). Our approach was a special case of Pollock's robust capture-recapture design where the probability that a bird does not sing is analogous to the probability that an animal is a temporary emigrant. Top models indicated that observers' detection probabilities were similar (0.78–0.84) if bobwhite were available, but bobwhite only had an approximately 0.61 probability of being available during a 2.5-minute sampling interval. Additionally, observers' detection probabilities increased substantially after the initial encounter with an individual bobwhite (analogous to a trap-happy response on the part of the observer). A simulated data set revealed that the combined method was precise when availability and detection given availability were substantially lower. Combined methods approaches can provide critical information for researchers and land managers to make decisions regarding survey length and personnel requirements for point-count-based surveys. |
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Keywords: | availability process Colinus virginianus dependent double-observer method detection probability North Carolina northern bobwhite perception process point counts Pollock's Robust Design time-of-detection method |
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