implications of the ivory-billed woodpecker rediscovery

I’ve been looking forward to reading Avian Conservation and Ecology, a new open-access electronic scientific journal sponsored by the Society of Canadian Ornithologists and Bird Studies Canada. I was not disappointed in the first issue, as it has an interesting and informative essay on the Ivory-billed Woodpecker entitled Rediscovering the king of woodpeckers: exploring the implications.[1]

The paper takes the rediscovery at face value. There’s not a consensus that this species was actually rediscovered, but that doesn’t take away from the point of the essay. In the introduction, authors Jeffrey Walters and Eileen Crist, both of Virginia Tech, note that “The emotion and exposure associated with the Ivory-billed Woodpecker’s plight guarantees that it will impact conservation in the United States, and perhaps elsewhere, far more than any other single species in the foreseeable future.”

The main question posed by the essay is, “Are the biological problems this case presents even solvable?”

These problems lie in two arenas: habitat and population size. The decline of the woodpeckers was due to habitat loss. Recovery of animals that have declined from this threat is much more difficult and less frequently achieved than recovery from threats that impact “vital rates” (e.g., reproductive decline due to pesticides). The challenge is compounded by the fact that the Ivory-billed Woodpecker has very large area requirements. It is often easier to address habitat quality versus habitat quantity. Acquiring lots of habitat often becomes a political hot potato,as is exemplified by the situations with California Gnatcatchers and Spotted Owls.

Second, the Ivory-billed Woodpecker, if it actually still exists, has a critically small population. Our general approach to endangered species management recognizes that small populations are extremely vulnerable to a host of threats. Our strategies aim for viable populations, which typically means a minimum of hundreds of individuals with as much genetic diversity as possible, spread over a geographic range that insulates against a catastrophic event wiping out the whole species. A rough “rule of thumb” is that a population of 500 is needed to maintain overall genetic variability. [2]

Is it even possible to restore a population of 500 Ivory-billed Woodpeckers? Other species have recovered, at least partially, from critically low numbers (the essay gives the Guam Rail and Takahe as examples), but these species had declined due to “vital rates” threats, and recovery efforts included captive breeding and translocation, which, the authors note, are techniques that are not possible with the Ivory-billed Woodpecker. If we settle for a smaller population, does that undermine current policy regarding the unacceptability of small populations?

The paper is fairly non-technical and short, give it a read. It is probably just the beginning of thoughtful analyses of the conservation implications surrounding the Ivory-billed Woodpecker.

Finally, there may be more news on the rediscovery. Mike’s Birding and Digiscoping Blog pointed out a post on Laura Erickson’s blog in which she hints at the fact that there may have been more sightings by the Cornell team in Arkansas; the statement was later changed, and when I went to look for it, I couldn’t find it at all.  Laura is on an Ivory-billed Woodpecker quest. It’s unclear whether she is part of an official Cornell team, but as I recall she has been in contact with them, or has a relative directly involved, or something like that.  Anyway, they may have asked her to edit or remove the post.  We’ll see.

[1] Walters, J. R., and E. L. Crist. 2005. Rediscovering the king of woodpeckers: exploring the implications. Avian Conservation and Ecology 1(1): 6. [online] URL: http://www.ace-eco.org/vol1/iss1/art6/

[2] Thompson, G.G. 1991. Determining Minimum Viable Populations under the Endangered Species Act. U.S. Dep. Commer., NOAA Tech. Memo. NMFS
F/NWC-198. 78 p.