Print PageThe detection of rare or endangered species based on evidentiary standards is an essential component of conservation biology programmes. In 2004, researchers announced the rediscovery of the ivory-billed woodpecker (Campephilus principalis), which was thought to have become extinct from its last redoubt in the southeastern United States in the 1940s. However, this report has been controversial because subsequent searches have so far failed to confirm its presence. Here we estimate the probability that the ivory-billed woodpecker persists today based on two independent and undisputed data sources: (1) museum specimens collected across the historic range of the species from 1850 to 1932; (2) contemporary avian census data from four of the most promising sites now being intensively searched for the woodpecker.
Results/Conclusions
From an analysis of the steeply declining collection curve of museum specimens, the estimate of persistence probability is less than 6.4 x 10-5, with a probable extinction date no later than 1980. Analysis of contemporary census data using estimators based on the cryptographic work of Alan Turing predicts that even a doubling of the census effort would reveal only 2-3 previously undetected species, but with no guarantee that the large and conspicuous ivory-billed woodpecker would be one of them. Both lines of evidence suggest that the probability that the ivory-billed woodpecker persists in 2011 is so low that substantial resources now devoted to searching for the woodpecker might be more productively allocated to other conservation priorities. The novel analytical methods developed here provide quantitative “stopping rules” that can guide efficient search efforts for other rare and missing species.
