IUCN / SSC Cat Specialist Group - Digital Cat Library |
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| MacKenzie, D.I.; Nichols, J.D.; Hines, J.E.; Knutson, M.G.; Franklin, A.B. | |
| Estimating site occupancy, colonization, and local extinction when a species is detected imperfectly | |
| 2003 Ecology (84): 2200-2207 | |
Few species are likely to be so evident that they will always be detected when present. Failing to allow for the possibility that a target species was present, but undetected, at a site will lead to biased estimates of site occupancy, colonization, and local extinction probabilities. These population vital rates are often of interest in long-term monitoring programs and metapopulation studies. We present a model that enables direct estimation of these parameters when the probability of detecting the species is less than 1. The model does not require any assumptions of process stationarity, as do some previous methods, but does require detection/nondetection data to be collected in a manner similar to Pollock's robust design as used in mark-recapture studies. Via simulation, we show that the model provides good estimates of parameters for most scenarios considered.We illustrate the method with data from monitoring programs of Northern Spotted Owls (_Strix occidentalis caurina_) in northern California and tiger salamanders (_Ambystoma tigrinum_) in Minnesota, USA. |
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