Tuesday, February 02, 2016
-- Speculatin' --
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I hear from skeptical sorts from time-to-time who clearly think (without saying it out loud ;-) that I'm a misguided idiot for keeping this blog going, and maintaining hope that IBWOs could possibly still persist.
Oddly... I beg to disagree ;-) (even as my confidence declines each passing year).
...Certain things though DO have to be accounted for, if Ivory-bills persist... and two I find particularly troubling are:
1) Why, after soooo many searches, over decades, as well as birders' repeated recreational presence in suitable areas, have there been so few direct encounters with Ivory-bills, especially close or lengthy such encounters? Even when birders flood into an area relatively quickly after a sighting, repeat sightings are rare???
2) Why, despite 100s of attempts (and millions of snapshots), has not a single clear Ivory-bill been captured on film by remote, automatic cameras trained on cavities and foraging sites deemed Ivory-bill-like? Even if humans can't encounter an IBWO, surely by now a robotic, automatic, non-tiring camera should've?
In the past I've offered two potential explanations to account for these dilemma and I'll re-state them here:
1) Possibly the vast majority of IBWO sightings are young, dispersing birds (or otherwise nomadic birds searching for new food sources) that don't actually reside in the territory where they are spotted. They are just passing through an area, but actually settling 25-100 miles away. And so, even if searchers flood into a locale following a sighting, they are simply searching the wrong place. While this might account for a lot of search failures, though, I'm doubtful it can account for all over the years.
2) My pet theory for awhile now is that remaining Ivory-bills have, through self-selection over decades, grown very wary of human activity. Both Noel Snyder and myself have hypothesized that it was hunting, and not habitat destruction, that finally drove IBWOs to near-extinction in their latter years, and the birds that survived would be those that learned to avoid humans.
The way to avoid humans is not only to inhabit remote woodland (which still gets visited by humans on occasion), but to occupy the most out-of-reach levels of that woodland -- the upper seasonally-leafy canopies of hardwoods; perhaps even spending more time inside cavities than was historically the case -- essentially out-of-sight of ground dwelling humans, who can, by the way, be kept under surveillance at great distance from such heights.
The birds might still visit ground-level for brief water or food excursions, but not to spend extensive time scaling bark, at a level that leaves them highly vulnerable, when perched. A lot of searches may simply be focusing on forest levels too low for where IBWOs spend perhaps 80-90% of their time (and the higher reaches are barely accessible to humans). There are several bird species that specialize in either upper or lower stories of forest habitat; why not the IBWO. (I previously had hopes for Mike Collins' novel tree-scaling methodology in the Pearl, but of course one individual can only cover a limited tract of area at any given time... and still can't see that well into leafed-out canopy). (...A separate, further problem, by the way, has been the frequent unreliability of most of the automatic camera systems deployed, even if we could actually recognize IBWO sign.)
It is always hugely speculative to hypothesize behavior changes in a species over time, but I think it also logical, and to-be-expected that any Ivory-bills remaining today, MUST have evolved changes from their early 20th century counterparts, or those few that Tanner witnessed at the Singer Tract. If they did not adapt such behaviors than I expect they are indeed extinct right now. (Even Tanner's Ivory-bills had likely evolved different behaviors from IBWOs populating North America a century or two earlier.)
If Ivory-bills are ever documented, the frustrated cry arising from the ornithology community will be, "How could this possibly be? HOW could we have missed them along the way!?" But some relatively small assumptions (about behavior and habitat requirements) can account for it... Nature is subtle, but persistent; humans on-the-other-hand are rarely as competent as we think we are. (Of course, if Ivory-bills are never indisputably documented, then yes, we "believers" will go down in history resembling 'misguided idiots.')
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8 comments:
I don't agree with Snyder in the broad sense, although I think hunting played a more important role than Tanner implied and suspect that wariness – whether learned, evolutionary, epigenetic, or some combination of the three – could be a factor. But so could scarcity and remoteness/difficulty of habitat.
I think it's reasonable to speculate about some behavioral changes, but ivorybill foraging behavior has major anatomical components, something that Snyder either didn't recognize or chose to ignore. This specialization exists in all the congeners, but the anatomical qualities are even more pronounced in the northern triad. This is not about dependence on old growth; it's about the location of the most abundant and nutritious food sources.
I hope to have more to say about this in a blog post, but your idea about forest level is a sledgehammer approach when a razor might be the more suitable implement. The birds will go where the food is, especially during breeding season, a time when human activity is relatively low, at least in Louisiana; squirrel season there, which runs from October - February and again in May, would actually have more people looking into the canopy than at other times of year. Other seasons that are on during that time frame are rabbit and turkey, where the focus is on the ground. In my experience in several parts of Louisiana, you really don't encounter many people in the woods after the end of January, after duck and deer seasons have closed.
Frankly, if I thought your theory were right, I'd have little hope for persistence.
Thanks for another interesting post.
I don't quite agree with the speculation that Ivory-bills are "spending more time inside cavities than was historically the case." It's my impression that the time that birds spend foraging is absolutely essential to their survival and not quite so malleable (see e.g., Woodpeckers of Eastern North America by L. Kilham for very detailed foraging accounts for several species of woodpeckers). I cannot imagine how the birds could alter their nutritional requirements is such a short span of time so that they could afford to simply hang out in cavities for a significantly greater portion of any given day than their relatively recent predecessors did out of fear of human predation.
With regard to wariness impacting foraging behavior, Imperial Woodpeckers were hunted to probable extinction, and they did not, (apparently by the accounts that I've read in the literature), develop a keen sense of foraging almost exclusively among the uppermost tree boughs in their habitat in order to avoid human predation. Why should Ivorybills be so different from Imperials in this regard? Further, some of the intriguing sightings reported over the years do not support the extreme wariness theory at all. In contrast, as far as I know, accounts of hunting over the past 50+ years do not support the idea of sustained attention by human predators against any remaining Ivorybills that would reinforce supposed hyper-vigilance in this species.
Your post brings to mind my experience with Pileated Woodpeckers in NYS over many years and how much rarer it has been for me to actually spot one as a visitor to forests in NYS than it has been to so readily observe them in the southeastern forests given the relative population densities in each area.
I still hold out hope for good quality video and great photos, someday, of Ivorybills similar to this one of a pair of Crimson Crested Woodpeckers https://www.flickr.com/photos/rgamboias/24028222076/in/faves-50708465@N00/.
A few more comments, following up on some of Bill's observations. There's evidence of hunting pressure in Cuba too, but the Lambs (late 1950s) observed ivorybills foraging at all levels there too.
>>>1) Why, after soooo many searches, over decades, as well as birders' repeated recreational presence in suitable areas, have there been so few direct encounters with Ivory-bills, especially close or lengthy such encounters? Even when birders flood into an area relatively quickly after a sighting, repeat sightings are rare???
The answer to the second question is complicated. Repeat sightings are not quite as rare as many believe. And other than Arkansas, I'm not really aware of birders "flooding into an area" after a sighting. For the first, I suppose it depends on what you mean by "repeated recreational presence". I've never run into a recreational birder in well over 100 field days, and I'd estimate that on the majority of those days I didn't into another person in the woods. Look at E-bird for a few Louisiana parishes, and you'll get a sense of how infrequently birded they are. In some, months can go by with no reports at all, and many of the same names crop up in multiple parishes.
>>>2) Why, despite 100s of attempts (and millions of snapshots), has not a single clear Ivory-bill been captured on film by remote, automatic cameras trained on cavities and foraging sites deemed Ivory-bill-like? Even if humans can't encounter an IBWO, surely by now a robotic, automatic, non-tiring camera should've?
As you point out yourself, there are issues with image quality, camera malfunction, etc. More importantly, finding the right target (that is a potential feeding tree that is still active or an active roost or nest) is an enormous challenge.
Continued below.
>1) Possibly the vast majority of IBWO sightings are young, dispersing birds (or otherwise nomadic birds searching for new food sources) that don't actually reside in the territory where they are spotted. They are just passing through an area, but actually settling 25-100 miles away. And so, even if searchers flood into a locale following a sighting, they are simply searching the wrong place. While this might account for a lot of search failures, though, I'm doubtful it can account for all over the years.
I think this is part of the problem. But again, you're conflating at least two things when referring to "search failures". In many instances, there have been multiple sightings, audio evidence, and accompanying suggestive photos/videos. The failure has been in obtaining incontrovertible proof, which has historically been and remains something of a moving target.
To add to Bill's comment about Pileated Woodpeckers, as abundant as they are in the southern forests and a vocally and aggressively they defend their territories, they're far more frequently heard than seen; they're far more frequently seen than seen well; they're far more frequently seen well than photographed well. I'll allow for some learned/evolved wariness as at least a possibility, but I think low numbers, light human traffic in prime habitats, and the documented lack of territoriality are the key factors.
The only photographs of ivorybills were taken after guides (Kuhn in Louisiana and Morgan Tindle in Florida) took ornithologists to known nesting grounds. Tanner only found birds in known, established home ranges; he failed utterly to find other birds he knew to be present. Allen and Kellogg (whose Florida photograph would almost surely be rejected as insufficient today) had this to say:
"On the other hand, failure to find the birds in a given area is no proof that they are not there, for they are not noisy except when disturbed; their voice does not carry nearly as far as that of the Pileated Woodpecker and in the big trees which they normally frequent they are easily overlooked. We camped for five days within three hundred feet of one nest and, except when the birds were about to change places on the nest or were disturbed, seldom heard them. We had great difficulty in following them through the woods to learn their feeding habits even after becoming very familiar with their notes. The senior author at one time stood under a giant oak and caught in his hand chips of bark and wood that an Ivorybill was scaling from a dead branch high in the tree without either one being able to see the other. We had hunted for three days for this particular pair of birds without ever hearing them, even though we were frequently within three hundred yards of the nest, which we finally found because we happened to be within hearing distance when the birds changed places on the nest."
Mark, you have done quite a bit of work on scaling. You have posted excessively on the subject as if the work was amounting to something important for the conservation of Ibwo.
Before you continue stating in multiple media channels that this work is somehow important or potentially pivotal can you please review or better yet have an actual scientist establish some reasonable abstract to be tested. Consistent well designed methods would be developed to test the abstract.
Since you have only recently contemplated, considered or discovered the potential foraging marks and behavior of an extremely common species, the gray squirrel, have you made a comprehensive list of all taxa that can potentially make ibwo sign on dead or live wood? The potential animals must of course include those with various appendages, bills, claws, teeth, etc. that have small widths to their bills but may simply be striking, chewing bark edges two or more times to imitate what you assume am ibwo bill mark would cause.
Also in the literature there are instances where field scientists have succinctly stated that where they have found ibwo they have noted extensive bark scaling. I for one wish we could go back to that reasonable standard of terseness rather than an attempt at field science presented as a long-running legal brief.
Tks sh
Looks to me like "sh" is back drinking the Jaegermeister and Tequila (mixed) again...
The REAL coyote... lol
The comment is totally off topic for this thread. It's a personal attack based on a straw man argument hidden behind anonymity, with an attempt to silence and a little dig at my legal background embedded in it. Google must be your friend or something, "sh". Charming stuff.
Scaling is not "important for the conservation of the IBWO", and I don't think I've ever written anything to suggest that's my view. I have said it's important as an indication of presence and a way of finding the bird. In addition to local guides, it's what the "field scientists" relied on back in the day.
I've listed the criteria more than once. Bill marks are a relatively minor component in the gestalt. Other than squirrels, there are no possible mammalian sources. For most of the work, the only plausible sources are PIWO and IBWO. The "reasonable standard of terseness" is part of the problem. I've spent over seven years trying to figure out exactly what is meant by "extensive bark scaling". And that's what I've written about. A lot of people like it. If you don't, no one's forcing you to read it.
And I am getting ongoing input from several actual scientists.
Tks
It says something about scientific rigor when after several years squirrel foraging that you were able to examine in your hand, at the "lab" and via photo files was still mis-ided as ibwo.
Now just days later you want us to be satisfied that not only the entire range of S. carolinensis work has been learned in a week but also niger, the larger fox squirrel. In addition there are other squirrel taxa implications (several subspecies).
Then its on to other mammals many of which survive seasonal flood events by becoming arboreal in times of limited food supply.
As you just asked of others where is the evidence?
Thanks
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