Inference about density and temporary emigration in unmarked populations

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Few species are distributed uniformly in space, and populations of mobile organisms are rarely closed with respect to movement, yet many models of density rely upon these assumptions. We present a hierarchical model allowing inference about the density of unmarked populations subject to temporary emigration and imperfect detection. The model can be fit to data collected using a variety of standard survey methods such as repeated point counts in which removal sampling, double‐observer sampling, or distance sampling is used during each count. Simulation studies demonstrated that parameter estimators are unbiased when temporary emigration is either “completely random” or is determined by the size and location of home ranges relative to survey points. We also applied the model to repeated removal sampling data collected on Chestnut‐sided Warblers (Dendroica pensylvancia) in the White Mountain National Forest, USA. The density estimate from our model, 1.09 birds/ha, was similar to an estimate of 1.11 birds/ha produced by an intensive spot‐mapping effort. Our model is also applicable when processes other than temporary emigration affect the probability of being available for detection, such as in studies using cue counts. Functions to implement the model have been added to the R package unmarked.

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Publication type Article
Publication Subtype Journal Article
Title Inference about density and temporary emigration in unmarked populations
Series title Ecology
DOI 10.1890/10-2433.1
Volume 92
Issue 7
Year Published 2011
Language English
Publisher Ecological Society of America
Publisher location Washington, D.C.
Contributing office(s) Patuxent Wildlife Research Center
Description 7 p.
First page 1429
Last page 1435
Country United States
State New Hampshire
Other Geospatial White Mountain National Forest
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