Sunday, December 14, 2008
-- Having It Both Ways --
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What the prior article on population dynamics calls to mind is the most trenchant argument skeptics make in the Ivory-bill debate. Can a creature have relatively few sightings over 60 years, with no sightings followed up by photographic documentation or definitive confirmation, and in fact still exist... OR, can a creature at very low population density successfully carry on reproductively for decades?... (The answer to both questions, singly, is indubitably yes.)
But the rub comes in combining the two questions (or as skeptics would say, 'trying to have it both ways' --- can there BOTH be so few IBWOs that they're rarely encountered, and yet enough to be reproductively viable for 60 years) --- the numbers of Ivory-bills must be just great enough (whatever that threshold is) to have at least maintained population stasis over decades (more recently they could be either increasing, or decreasing), and yet scarce enough to help account for the overall paucity of sightings and difficulty of photography. It is a somewhat fine line and balancing act, but yet once again, given the habitat and habits and history of the Ivory-billed Woodpecker (an upper canopy and cavity-dwelling flying creature of deep forest) it is much more plausible with this species than it would be for many others --- indeed, it is easily as plausible, as the notion of every single sighting since 1950 being written off as a 'mistake.' And it is funny how often in nature if something is possible, it occurs (sort of the inverse of 'Murphy's Law').
Finally, in another "stay-tuned" story, Mark Bailey sends along this report of supposedly-extirpated pumas in Alabama.
Addendum: Mark seems to have taken this story down; I assume this means its authenticity (which he was trying to check on) did not check out; or if he re-posts it, I'll mention it again here.
Addendum II : Mark confirms now he has determined picture and story to be a hoax.
He now has this explanatory post up on the matter.
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6 comments:
it is easily as plausible, as the notion of every single sighting since 1950 being written off as a 'mistake.'
Not at all. There are rational reasons why confidence in the Auburn and Cornell sightings have plummeted. Common sense dictates that if the birds are actually there and seen repeatedly as has been reported, that eventually someone would get a good photograph. Common sense dictates that if no one can prove at any time by any means that the bird lives, combined with the scores of proven false reports, the bird likely no longer exists.
"combined with the scores of proven false reports, the bird likely no longer exists."
Where does this come from , and by what means have these reports been proven false?
Fleeting glimpses: I had a sighting that lasted for 7-8 minutes.
Expectation bias: I was scouting for ducks not looking for woodpeckers.
The world's leading woodpecker expert claims Arkansas has the highest Pileated concentration on earth. Imagine trying to find 1 red jellybean with a white stripe out of a jar of hundreds of plain red jellybeans. That should give you a slight idea of what this search is like.
Heaven knows how many times someone has excitedly called up a birding expert saying they've just seen an Ivory-bill. After questioning it becomes clear they've seen a Pileated. Many times people have brought in photos of Ivory-bills except they turn out to be Pileateds. Ask Cornell how many reports they get and how many they feel worthy of following up on. Scores of false reports is stating it conservatively.
A few lucky ones in recent times have claimed long sightings. But they always either don't have a camera or they don't take photos for some reason. I don't think it's a coincidence that there are no good sightings when someone has a camera and the ability to take the photo.
A person doesn't have to be lying to make an honest mistake, even with a long, good view.
Hello Ross
I've often wondered if you ever kept notes of the actual conversation you had on the phone with your friend during the "long sighting"?
And if you did, are you going to publish them?
Peter in Ireland
By the above argument there would never be anomalies in science -- it is a false generalization to imply that because something holds in most cases it ought automatically be presumed the case in ALL cases. Every Ivory-bill sighting essentially needs to be adjudged independently (and yes, most will be falsified), otherwise you are simply injecting a strong bias for dismissal into the equation from the start (which than feeds on itself) --- don't judge B's sighting based on what happened with X, Y, and Z's sightings, no matter how tempting it is to do so; there are too many independent variables separating each case to lump them together.
It's a tad like the 'gambler's fallacy' where people surmise say the tenth toss of a fair coin based on the results of the previous nine tosses, but it's not valid to do so.
"It's a tad like the 'gambler's fallacy' where people surmise say the tenth toss of a fair coin based on the results of the previous nine tosses, but it's not valid to do so."
Hardly. With a coin with two sides the odds are 50/50. If a coin that may or may not have a heads at all gets flipped for 60 years without a verified "heads" I can be pretty sure there's no heads on the coin.
"Imagine trying to find 1 red jellybean with a white stripe out of a jar of hundreds of plain red jellybeans. That should give you a slight idea of what this search is like."
I can imagine it easily. I guarantee I could find and photograph that white striped jelly bean. I guarantee I couldn't find and photograph an Ivory-bill.
Cornell is (was) SURE they have a video of an Ivory-bill. Nearly all other experts say they either can't tell or it's definitely a Pileated. Cornell had identified unique bark scaling that was almost certainly made by Ivory-bills. Automatic cameras showed otherwise. Cornell recorded sounds reported to be unique to Ivory-bills. Turned out not to be true.
I use patterns and experience to make rational decisions in the real world. Show me someone who now "believes" in the Ivory-bill after studying all the evidence, and I'll show you someone who wants to believe in the Ivory-bill.
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