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In a comment on the previous post, "Steve" essentially asks WHAT will it take for some of us to conclude that the Ivory-bill is no more? I was going to respond in the comments (and now Jacob has) but it deserves a separate (more long-winded) post, since it's such a common question:
The basic answer is pretty simple... you send capable folks out to areas that a species might conceivably remain in (or actually have been sighted) and do a reasonably thorough, organized search... AND come up empty-handed... NO credible sightings, nor signs of the bird's presence. THAT would be indicative of possible extinction. You can't prove extinction; you can only keep amassing more and more data toward its support.
If such searches were conducted for the Dodo, or Moa, or even Passenger Pigeon, most likely there would be nothing to show for it. But in the case of the Ivory-bill almost every such large scale search results in (even if skeptics don't acknowledge it) a few sightings claims from credentialed, credible individuals, and additional possible signs of the bird (foraging signs, cavities, auditory encounters) -- if there were sightings with NO such other evidence, it would be more difficult to take the sightings seriously... OR, if there were signs, but without ever any sightings, the signs could be easily written off; but the fact that both types of evidence occur on rare, yet repeated occasions, makes it more difficult to simply ad hoc (because it fits a preconceived hypothesis), label them all 'mistakes' and misidentifications. Indeed, as I've argued previously, if mistakes are this easy and prevalent in birding then doing bird counts and censuses must be a futile waste of time, they would be so heavily flawed in regards to look-alike birds (and the majority of birds have look-alikes). [Indeed, many argue that the actual raw data of bird counts is hugely erroneous (both unreliable and invalid), and the only real worth derives from looking at relative trend figures over extended periods of time.]
Nor does it matter if there are 5000 other individuals with little credibility or experience who erroneously report IBWOs; you can't automatically generalize from such known instances to all cases, but must view each case individually on its own merits (or lack thereof).
Yes, it is hugely troublesome that these unconfirmed claims have been going on for 60+ years without verification or better photographic evidence. And frustrating too that claims still come from widely disparate areas -- almost certainly there can't be that many separate populations of IBWO left. I understand why the likes of Paul Sykes, Jerry Jackson, and others have largely given up hope that such claims make much sense any longer, no matter how credible or certain any given observer. When every followup seems to fail to definitively confirm the birds once-and-for-all, it is easy to conclude that a telling pattern is evident.
I continually have to ask though, if a bird is truly incredibly rare, possibly even hanging on by a thread, residing in remote, difficult habitat (not well-frequented by birders), living principally high up in tree canopies and within cavities, possibly wary of humans, and capable of rapid long-distance flight... then what would the evidence, if any, for its existence look like -- and maybe, perhaps, just possibly, it might look very similar to that which we have before us. The best explanatory fit and best odds for the entire panoply of evidence at hand may still be that a few Ivory-bills swoop and kent and double-knock somewhere in a dense quarter of the American Southeast.
...Or, not. The limits of my own patience do creep closer with each passing year.
And here's the story of another bird species (the Jerdon’s Courser) that relates somewhat to this whole discussion:
http://www.downtoearth.org.in/content/lives-others?page=0,3 ------------------------------------------------------------------------
1 comment:
Well written in my opinion. I certainly hope I find something qualitative(?) in my Bachman's Warbler searches to bring that back from the commonly held view of extinction. In time, though, this will all be settled. In, I would imagine, no more than 10 years we will find something conclusive, because the population of IBWOs (provided they are around) should be getting to the point that it will be almost impossible for them to go unseen, and also, perhaps the birds will warm up to some of the searchers such as Mike Collins who frequent the swamps, thus increasing the chances of someone photographing the birds.
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