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Using Search Time and Regression to Estimate Abundance of Territorial Spotted Owls
Author(s) -
Ward James P.,
Franklin Alan B.,
Gutierrez R. J.
Publication year - 1991
Publication title -
ecological applications
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.864
H-Index - 213
eISSN - 1939-5582
pISSN - 1051-0761
DOI - 10.2307/1941813
Subject(s) - abundance (ecology) , statistics , ecology , sampling (signal processing) , population , regression , regression analysis , geography , variance (accounting) , biology , demography , mathematics , computer science , accounting , filter (signal processing) , sociology , business , computer vision
Using conventional sampling methods, unbiased, precise estimates of the number of individuals in a population can be difficult to obtain for rare, secretive species. We used a Leslie regression model (ARM) to estimate the number (N 0 ) and the variance of the number (V[N 0 ]) of adult and subadult Northern Spotted Owls in a territorial population from direct counts within a 292 km 2 study area. Estimates of N 0 from day counts were more accurate and precise and more robust to fluctuations in survey effort than estimates from night counts. ARM estimates from day counts were not significantly different from two different maximum—likelihood estimates and required 30—64% less effort. These findings suggest a less costly method for statistically comparing Spotted Owl abundance between spatial or temporal units.