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IVORY-BILLS  LiVE???!  ...

=> THE blog devoted to news and commentary on the most iconic bird in American ornithology, the Ivory-billed Woodpecker (IBWO)... and... sometimes other schtuff.
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"....The truth is out there."

-- Dr. Jerome Jackson, 2002 (... & Agent Fox Mulder)

“There are more things in heaven and earth, Horatio, than are dreamt of in your philosophy.”

-- Hamlet

"All truth passes through 3 stages: First it is ridiculed. Second, it is violently opposed. Third, it is accepted as self-evident."

-- Arthur Schopenhauer






Thursday, October 18, 2007

 

-- More Old Ground --


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Covering some old ground once again....

The lack of confirmation for various Ivory-billed Woodpecker claims over the decades, lack of a definitive photograph in 60 years, and failure to find an active nesthole, are all excellent reasons for postulating that Ivorybills are very rare creatures indeed, but insufficient for proposing extinction of the species, without a more thorough and systematic search of habitat, as now underway. The potential sheer rarity of the species can adequately explain all these (lack of) findings.

The strongest argument skeptics can muster for extinction is probably what I'll term the 'bottleneck' argument --- i.e., that one can't both assume the species is so rare that it exists only in small isolated, disparate populations, and yet simultaneously believe it has managed to persist for 60 years, through the breeding or genetic 'bottlenecks' that would result --- Either the population must be (or have been) much larger to still be around today (in which case good, confirmed sightings and/or photos would be available by now), or, if so rare for decades that it couldn't be documented, than individuals simply couldn't persist to today --- you can't have it both ways... To which I simply reply, "schnickerdooooodles!!"

The reproductive drive of animals is incredibly powerful (and mysterious). Moths of course employ pheromones to traverse amazing distances in locating mates, and larger creatures as well, routinely defy odds to link up with their own kind. Tanner presumed at the time of his study that there were small populations of IBWO in Louisiana, Florida, and S. Carolina. He may have underestimated the numbers and locales, but even if he was correct that presents both potential Atlantic Coast and Gulf Coast corridors for Ivorybills to move along in pursuit of mates and territory --- corridors, that since the 50's have gotten slowly but steadily richer in (second-growth) habitat. Ivorybills were known as strong fliers that could easily cover wide distances, even if not migratory by nature. And with hunting pressure off them, odds for survival could further increase.

Moreover (as I've said previously), under some circumstances, animal populations can actually drop much faster from say 1000 individuals to 500, or 500 to 200, than from 50 to 0, because at the lower numbers, 'sustainability' sets in; i.e., the number of individuals being produced over a given time period offsets the number being lost, once territory, food, and other needs can now be met easily at the lower densities involved. (Whooping Cranes were down to around 14 individuals before humans stepped in to turn their situation around --- I don't know if there are any records indicating just how long they hung on at the under-40 level before that human intervention took place? --- cranes of course are very different from woodpeckers, but if they could sustain a viable population for decades,
while only raising one chick per year in the wild, before Man stepped in, than the IBWO would seem to have the same opportunity.)

So, could the Ivorybill sustain itself at such small numbers over a lengthy period as to elude being definitively documented? Obviously, my answer is yes. How probable is it? --- I don't know (...maybe just as probable as every last report of the species over 5 decades being in error?).... and afterall really, in the grander scheme of things, how probable is a giraffe or a duck-billed platypus??? Or, as Annie Dillard reminds us, "improbabilities" are the "stock and trade" of nature....
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