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The Ivory-bill after a decade: Just how do we know when a species is extinct?

Eskimo Curlew, hand-colored engraving by John James Audubon (1785–1851), Wikimedia Commons. The shorebird was last recorded on Galveston Island, Texas, in 1962, over 50 years ago.
Eskimo Curlew, hand-colored engraving by John James Audubon (1785–1851), Wikimedia Commons. The shorebird was last recorded on Galveston Island, Texas, in 1962, over 50 years ago.

In 2010 and 2012, five teams of researchers published studies in which they concluded either that the Ivory-billed Woodpecker was extinct or that the odds of finding a living Ivory-bill were less than 1 in 15,625.

By what procedure is a species formally declared extinct? How long must we wait before we know it is no more?

According to the Committee on the Status of Endangered Wildlife in Canada (COSEWIC Assessment Process, Categories and Guidelines), a species may be judged extinct or extirpated if one of three conditions is met:

  • If there exists no remaining habitat and there have been no records of the species despite recent surveys
  • If 50 years have passed since the last credible record of the species, despite surveys in the interim
  • Or if there is sufficient information to document that no individuals of the species remain alive.

Certainty is harder to come by in the United States and in the eyes of the International Union for Conservation of Nature, publisher of the widely accepted IUCN Red List of Threatened Species.

According to the IUCN, a species may be called extinct when “no reasonable doubt” remains that the last individual has died:

“A taxon is presumed Extinct when exhaustive surveys in known and/or expected habitat, at appropriate times (diurnal, seasonal, annual), throughout its historic range have failed to record an individual. Surveys should be over a time frame appropriate to the taxon’s life cycle and life form.” (2001 Categories & Criteria, version 3.1)

In the United States, where the Fish and Wildlife Service is required to survey the status of each animal listed under the Endangered Species Act at least once every five years, the official guidance is even vaguer:

“Unless all individuals of the listed species had been previously identified and located, and were later found to be extirpated from their previous range,” write federal regulators, “a sufficient period of time must be allowed before delisting to indicate clearly that the species is extinct.” (50 CFR 424.11 – Factors for listing, delisting, or reclassifying species)

The last universally accepted sighting of the Ivory-billed Woodpecker was by artist Donald Eckelberry in northeastern Louisiana in April 1944.

A version of this article accompanied a 10-page special report on the Ivory-billed Woodpecker written by Jerome A. Jackson. The report appeared in the February 2015 issue of BirdWatching. Subscribe.

Read more about the Ivory-billed Woodpecker

Truth is out there
Jerome A. Jackson assesses David Kulivan’s 1999 report of Ivory-billed Woodpeckers in the Pearl River Swamp, Louisiana. June 2002.

Old friend found
Eyewitness accounts of sightings of Ivory-billed Woodpeckers from the Cache River, Arkansas. By Chris Niskanen, August 2005.

Now what?
What’s next for the Big Woods Conservation Partnership and the Ivory-billed Woodpecker. By Elliott Swarthout and Ron Rohrbaugh, August 2005.

First step
In the wake of the Ivory-billed Woodpecker rediscovery, a plea for conservation of the world’s other declining species. By George Fenwick, August 2005.

Old friend missing
Description, range, habits, and credible sightings of the Imperial Woodpecker. By Matt Mendenhall, December 2005.

Faith-based ornithology
Jerome A. Jackson argues that mistakes were made, putting support for future conservation at risk. By Chuck Hagner, February 2006.

The other guys
Geoffrey Hill describes his search for the Ivory-billed Woodpecker along the Choctawhatchee River in Florida. February 2007.

1 in 15,625
Teams of researchers calculate the odds of finding a living Ivory-bill today. By Matt Mendenhall, February 2012.

Ghost bird
Ten years after Ivory-bill fever swept the nation, Jerome A. Jackson assesses the hope, hype, and disappointment. February 2015.

Sightings map
Historic ranges and reported sightings of Ivory-billed Woodpeckers since 1944. By BirdWatching Magazine, August 2005, February 2015.

The Ivory-bill after a decade: $20.3 million spent, total cost ‘unknown.’

  Originally Published

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