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Mitchell Baker, Nadav Nur, Geoffrey R. Geupel, Correcting Biased Estimates of Dispersal and Survival Due to Limited Study Area: Theory and an Application Using Wrentits, The Condor: Ornithological Applications, Volume 97, Issue 3, 1 August 1995, Pages 663–674, https://doi.org/10.2307/1369175
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Abstract
Accurate estimates of dispersal distributions and survival to breeding are essential for estimating gene flow and population demographics, and for testing the predictions of mechanistic models. We derive a method that corrects for the underestimate of dispersal and survival inherent in studies conducted within a finite area. Each dispersal event is weighted by the inverse of the probability of observing that event, calculated by dividing the observable dispersal events of a given distance by all possible dispersal events of that distance. The method takes into account the shape of the study area and suitability of habitat. The method is applied to a twelve-year field study of natal dispersal in Wrentits (Chamaea fasciata) resulting in an increase in the estimate of mean and median dispersal from observed values of 267 and 248 m to corrected values of 375 and 387 m. The correction method also estimates the number of second year birds recruiting to potential breeding territories on and off the study area. Seventy-five of the 799 locally born fledglings recruited onto the study plot (9.3%). We estimate that an additional 101 birds recruited off the study plot, increasing the estimate of yearling survival to recruitment from 9.3% to 21.9% of young fledged. We used a simulation approach to generate testable predictions that validate the assumptions and results of the method. The method is easy to apply, and is easily extended to incorporate greater realism and detail.
