Specimen‐Based Modeling,Stopping Rules,and the Extinction of the Ivory‐Billed Woodpecker |
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| Authors: | NICHOLAS J. GOTELLI ANNE CHAO ROBERT K. COLWELL WEN‐HAN HWANG GARY R. GRAVES |
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| Affiliation: | 1. Department of Biology, University of Vermont, Burlington, VT 05405, U.S.A., email ngotelli@uvm.edu;2. Institute of Statistics, National Tsing Hua University, Hsin‐Chu 30043, Taiwan;3. Department of Ecology and Evolutionary Biology, University of Connecticut, Storrs, CT 06269‐3043, U.S.A.;4. Department of Applied Mathematics, National Chung Hsing University, Tai‐Chung 402, Taiwan;5. Department of Vertebrate Zoology, MRC‐116, National Museum of Natural History, Smithsonian Institution, PO Box 37012, Washington, D.C. 20013‐7012, U.S.A., and Center for Macroecology, Evolution, and Climate, University of Copenhagen, Denmark |
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| Abstract: | Abstract: Assessing species survival status is an essential component of conservation programs. We devised a new statistical method for estimating the probability of species persistence from the temporal sequence of collection dates of museum specimens. To complement this approach, we developed quantitative stopping rules for terminating the search for missing or allegedly extinct species. These stopping rules are based on survey data for counts of co‐occurring species that are encountered in the search for a target species. We illustrate both these methods with a case study of the Ivory‐billed Woodpecker (Campephilus principalis), long assumed to have become extinct in the United States in the 1950s, but reportedly rediscovered in 2004. We analyzed the temporal pattern of the collection dates of 239 geo‐referenced museum specimens collected throughout the southeastern United States from 1853 to 1932 and estimated the probability of persistence in 2011 as <6.4 × 10?5, with a probable extinction date no later than 1980. From an analysis of avian census data (counts of individuals) at 4 sites where searches for the woodpecker were conducted since 2004, we estimated that at most 1–3 undetected species may remain in 3 sites (one each in Louisiana, Mississippi, Florida). At a fourth site on the Congaree River (South Carolina), no singletons (species represented by one observation) remained after 15,500 counts of individual birds, indicating that the number of species already recorded (56) is unlikely to increase with additional survey effort. Collectively, these results suggest there is virtually no chance the Ivory‐billed Woodpecker is currently extant within its historical range in the southeastern United States. The results also suggest conservation resources devoted to its rediscovery and recovery could be better allocated to other species. The methods we describe for estimating species extinction dates and the probability of persistence are generally applicable to other species for which sufficient museum collections and field census results are available. |
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| Keywords: | avian censuses Campephilus principalis extinction estimation extinction probability Ivory‐billed Woodpecker museum specimens species richness estimators stopping rules Campephilus principalis censos aviares especí menes de museo estimació n de la probabilidad de extinció n estimadores de la riqueza de especies reglas de decisió n |
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