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Ivory-bill expert Jerome Jackson and Arkansas Ivory-bill sighter/author Tim Gallagher were interviewed on National Public Radio's "Living On Earth" today; nothing much new in their answers, but still of interest as we await internet publication of the Jackson et.al. critique of the Arkansas evidence (supposedly to be out by end of this month).
In the meantime, the Ivory-bill 'recovery' team is making plans for an organized widespread search for the species this winter, not only in the northeast woods of Arkansas, but in potential habitat throughout the Ivory-bill's old range stretching from the Carolinas to Texas. It's about time such an endeavor was undertaken!
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Friday, July 29, 2005
Tuesday, July 26, 2005
"Bootstrap Analysis" weblog
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Another good post/update from "bootstrap analysis" weblog regarding controversy over the Arkansas sightings, prior to release of the critics' paper:
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Another good post/update from "bootstrap analysis" weblog regarding controversy over the Arkansas sightings, prior to release of the critics' paper:
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Monday, July 25, 2005
- Arkansas Sightings Controversy -
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A good discussion of the forthcoming Prum, Robbins & Jackson paper critical of the Arkansas IBWO sightings can be found at "Bootstrap Analysis" weblog.
I'll have more to say about the critics' paper once it is published and their specific wording and arguments can be scrutinized. Until then, it is unfortunate that to many the approach the authors have taken does give off an appearance (whether real or not) of 'sour grapes'. Should be some interesting discussions ahead.
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A good discussion of the forthcoming Prum, Robbins & Jackson paper critical of the Arkansas IBWO sightings can be found at "Bootstrap Analysis" weblog.
I'll have more to say about the critics' paper once it is published and their specific wording and arguments can be scrutinized. Until then, it is unfortunate that to many the approach the authors have taken does give off an appearance (whether real or not) of 'sour grapes'. Should be some interesting discussions ahead.
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Sunday, July 24, 2005
- A FEW THINGS WORTH NOTING and FURTHER SPECULATIONS --
1. In its heyday the Ivory-billed Woodpecker resided in upland pine forests in Cuba, cypress swamps in Florida, and bottomland mixed hardwoods in Louisiana and elsewhere -- three somewhat different habitats. This was almost certainly a more adaptable species than often portrayed. For food and nesting purposes, yes, it did need relatively large, mature tracts of forest, but setting and tree-type may not have been strict limiting factors even if the bird had preferences.
2. Similarly, the few studies of Ivory-bill stomach contents available indicated that the species’ diet was about 60% vegetable matter and 40% or less animal matter and only a small percentage of the animal portion consisted of the wood-boring beetle larvae which Tanner pointed to as yet a further ‘specialization’ of this bird. In short, while Ivory-bills clearly enjoyed certain components of their diet when available, it is again less clear how necessary those components were for survival, the bird likely being more of a feeding ‘generalist’ than implied in much of the literature (indeed, no other woodpecker or bird species sharing the same habitat of the Ivory-bill appeared to have any such ‘specialized’ dietary needs, and one is left to wonder why the Ivory-bill would be different).
In short, unlike the tentative conclusions that Tanner reached which later hardened into repeated standard presumptions, the Ivory-bill may have been an adaptable species if only given enough time and solitude to do so.
3. Ivory-bills were widely hunted for food, ornamental purposes, and for both private and public collections/dis-plays (and their eggs collected as well). It is impossible to know just how many individual birds fell victim to this fate. Tanner believed hunting was second only to habitat loss in its effect on the species’ population. I believe, even at that, the overall impact of hunting may be vastly underestimated, given that Ivory-bills were never abundant to begin with, and given what relatively easy and tempting targets they would have made, always returning to the same roost or nest trees. As relatively long-lived birds (estimated 10 to 20+ year lifespan), laying 3-5 eggs per nest, Ivory-bills had ample opportunity to more than ‘replace’ themselves in their lifetimes (only two offspring reaching maturity required to replace a living pair), except when hunting cut their lives short.
4. The discovery of the species in the state of Arkansas is especially noteworthy as Arkansas was rarely high on lists of promising search locales. Florida, Mississippi, and Louisiana, were better prospects in most searchers’ minds. South Carolina and Texas were likely better as well. Georgia and Alabama remain yet other potential states for hidden Ivory-bills. But significantly, finding the Ivory-bill in Arkansas, at the northern end of its one-time range, opens the door wide to yet other little-looked-at possibilities, including southern Missouri, southern Illinois, Tennessee, and Kentucky. In short, besides Arkansas there are probably 10 or more states bearing some potential of harboring Ivory-bills. This is a bird that has had 60+ years to wander in search of food and habitat, and there is little basis for assuming it must be restrained to its former 200 year-ago range boundaries.
There is no large ‘corridor’ of dense forest left in the south for the Ivory-bill to move along as existed in the nation’s early days. Yet for Ivory-bills to still be found at all today implies that far greater numbers persisted in various locales in the 1930’s than Tanner estimated. There likely existed (both then and now) forest ‘patches’ in multiple states that were adequate to sustain one or two pair of the species, such that offspring could mature before dispersing out to seek new such patches for themselves. (Indeed one of the most intriguing facts to this writer has long been the number of scoffed-at ‘sightings’ in previous decades occurring near or over major roadways/highways, NOT in deep woods -- individual birds dispersing to new areas, perhaps???). In this way, small numbers of Ivory-bills would be ‘hop-scotching’ around the south for the last century, not just gradually inching toward some final strong-hold. With hunting and collecting pressure finally off the birds, the existence of such patches might well be sufficient to permit a population to stabilize and commence a comeback (Ivory-bills having few predators in the past other than Man). And, as Jerome Jackson has oft-noted, thanks to conservation efforts and revised forestry practices, there is literally MORE suitable (2nd and 3rd-growth) habitat available for the Ivory-bill today in the U.S. than existed decades ago at the height of forest destruction.
The ‘will to live’ and to reproduce is a persistent, potent force among living things. While the shooting of Ivory-bills essentially took individuals out of the population immediately, habitat loss, per se, had NO SUCH immediate effect for a creature that needed only to flap its wings to seek out new territory and then make new adaptations issuing from that ‘will to live.’ The genes and behaviors of any birds thusly adapting might then be passed on to a new generation, however few in number. We have, in essence, a 70-year unaccounted-for gap in our knowledge since the last known population of Ivory-bills at the Singer Tract was studied. A gap of hugely unacknowledged uncertainties.
In short, the likelihood that several dozen Ivory-bills persist in southern wilds seems to this writer FAR GREATER than the probability that humans, in our clumsiness, have stumbled upon the last 1 or 2 in existence. Based on previous distribution pattern, report history, remaining habitat, and time elapsed I would be surprised if at least half of the following states don’t harbor pockets of Ivory-bills: Florida, Georgia, Alabama, Louisiana, Missississipi, Arkansas, Texas, South Carolina, North Carolina, Tennessee, Kentucky, Missouri, Illinois, and Virginia. Actually finding the shy, elusive birds anytime soon however, is another matter entirely, for which I hold less optimism, although re-kindled interest in the species will help. ...One must even wonder if the birds may be better off UN-found. Or can we humans at long last do right by this iconic creature of the American South; this majestic and aloof phantom of the forest depths? ...Lord God, one hopes so!
(the above is adapted from material previously published in The Chapel Hill Bird Club Bulletin.)
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1. In its heyday the Ivory-billed Woodpecker resided in upland pine forests in Cuba, cypress swamps in Florida, and bottomland mixed hardwoods in Louisiana and elsewhere -- three somewhat different habitats. This was almost certainly a more adaptable species than often portrayed. For food and nesting purposes, yes, it did need relatively large, mature tracts of forest, but setting and tree-type may not have been strict limiting factors even if the bird had preferences.
2. Similarly, the few studies of Ivory-bill stomach contents available indicated that the species’ diet was about 60% vegetable matter and 40% or less animal matter and only a small percentage of the animal portion consisted of the wood-boring beetle larvae which Tanner pointed to as yet a further ‘specialization’ of this bird. In short, while Ivory-bills clearly enjoyed certain components of their diet when available, it is again less clear how necessary those components were for survival, the bird likely being more of a feeding ‘generalist’ than implied in much of the literature (indeed, no other woodpecker or bird species sharing the same habitat of the Ivory-bill appeared to have any such ‘specialized’ dietary needs, and one is left to wonder why the Ivory-bill would be different).
In short, unlike the tentative conclusions that Tanner reached which later hardened into repeated standard presumptions, the Ivory-bill may have been an adaptable species if only given enough time and solitude to do so.
3. Ivory-bills were widely hunted for food, ornamental purposes, and for both private and public collections/dis-plays (and their eggs collected as well). It is impossible to know just how many individual birds fell victim to this fate. Tanner believed hunting was second only to habitat loss in its effect on the species’ population. I believe, even at that, the overall impact of hunting may be vastly underestimated, given that Ivory-bills were never abundant to begin with, and given what relatively easy and tempting targets they would have made, always returning to the same roost or nest trees. As relatively long-lived birds (estimated 10 to 20+ year lifespan), laying 3-5 eggs per nest, Ivory-bills had ample opportunity to more than ‘replace’ themselves in their lifetimes (only two offspring reaching maturity required to replace a living pair), except when hunting cut their lives short.
4. The discovery of the species in the state of Arkansas is especially noteworthy as Arkansas was rarely high on lists of promising search locales. Florida, Mississippi, and Louisiana, were better prospects in most searchers’ minds. South Carolina and Texas were likely better as well. Georgia and Alabama remain yet other potential states for hidden Ivory-bills. But significantly, finding the Ivory-bill in Arkansas, at the northern end of its one-time range, opens the door wide to yet other little-looked-at possibilities, including southern Missouri, southern Illinois, Tennessee, and Kentucky. In short, besides Arkansas there are probably 10 or more states bearing some potential of harboring Ivory-bills. This is a bird that has had 60+ years to wander in search of food and habitat, and there is little basis for assuming it must be restrained to its former 200 year-ago range boundaries.
There is no large ‘corridor’ of dense forest left in the south for the Ivory-bill to move along as existed in the nation’s early days. Yet for Ivory-bills to still be found at all today implies that far greater numbers persisted in various locales in the 1930’s than Tanner estimated. There likely existed (both then and now) forest ‘patches’ in multiple states that were adequate to sustain one or two pair of the species, such that offspring could mature before dispersing out to seek new such patches for themselves. (Indeed one of the most intriguing facts to this writer has long been the number of scoffed-at ‘sightings’ in previous decades occurring near or over major roadways/highways, NOT in deep woods -- individual birds dispersing to new areas, perhaps???). In this way, small numbers of Ivory-bills would be ‘hop-scotching’ around the south for the last century, not just gradually inching toward some final strong-hold. With hunting and collecting pressure finally off the birds, the existence of such patches might well be sufficient to permit a population to stabilize and commence a comeback (Ivory-bills having few predators in the past other than Man). And, as Jerome Jackson has oft-noted, thanks to conservation efforts and revised forestry practices, there is literally MORE suitable (2nd and 3rd-growth) habitat available for the Ivory-bill today in the U.S. than existed decades ago at the height of forest destruction.
The ‘will to live’ and to reproduce is a persistent, potent force among living things. While the shooting of Ivory-bills essentially took individuals out of the population immediately, habitat loss, per se, had NO SUCH immediate effect for a creature that needed only to flap its wings to seek out new territory and then make new adaptations issuing from that ‘will to live.’ The genes and behaviors of any birds thusly adapting might then be passed on to a new generation, however few in number. We have, in essence, a 70-year unaccounted-for gap in our knowledge since the last known population of Ivory-bills at the Singer Tract was studied. A gap of hugely unacknowledged uncertainties.
In short, the likelihood that several dozen Ivory-bills persist in southern wilds seems to this writer FAR GREATER than the probability that humans, in our clumsiness, have stumbled upon the last 1 or 2 in existence. Based on previous distribution pattern, report history, remaining habitat, and time elapsed I would be surprised if at least half of the following states don’t harbor pockets of Ivory-bills: Florida, Georgia, Alabama, Louisiana, Missississipi, Arkansas, Texas, South Carolina, North Carolina, Tennessee, Kentucky, Missouri, Illinois, and Virginia. Actually finding the shy, elusive birds anytime soon however, is another matter entirely, for which I hold less optimism, although re-kindled interest in the species will help. ...One must even wonder if the birds may be better off UN-found. Or can we humans at long last do right by this iconic creature of the American South; this majestic and aloof phantom of the forest depths? ...Lord God, one hopes so!
(the above is adapted from material previously published in The Chapel Hill Bird Club Bulletin.)
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-- SOME HISTORY --
James Tanner wrote the “definitive” study of Ivory-billed Woodpeckers in N. America in 1942 as a doctoral thesis at Cornell. His is a meticulous and wonderful study of... the half-dozen-or-so Ivory-bills he specifically observed over time at the Singer Tract in Louisiana. While he gathered information and anecdotes on Ivory-bills from throughout the Southeast, Tanner’s actual observations were retricted to a small sample of birds at a single La. location, making the generalizability of his findings and conclusions somewhat suspect. Conclusions about Ivory-bill behavior, and dietary and habitat needs are based largely upon what the birds at the Singer Tract appeared to utilize and enjoy, which is NOT NECESSARILY the same as what the species REQUIRED for survival.
As Tanner himself stated, so accurately,
“The chief difficulty of the study has been that of drawing conclusions from relatively few observations... entirely confined to a few individuals in one part of Louisiana... The conclusions drawn from them will not necessarily apply to the species as it once was nor to individuals living in other areas.”
Yet, in ensuing years these words were largely ignored as ornithologists turned Tanner’s doctoral work into gospel criteria for all Ivory-billed Woodpeckers.
At the time of his studies, Tanner concluded that fewer than 30 Ivory-bills remained in the entire Southeast scattered amongst just three states: Louisiana, Florida, and S. Carolina. In fact, some believe there may have been 200+ Ivory-bills left in the 30’s dispersed across far more locales in very small groups. Further, Tanner believed a single pair of the birds needed a minimum of 6 square miles of forest tract for survival even though the only slightly smaller-sized Pileated could reside on far less territory. Almost certainly non-breeding, juvenile Ivory-bills could make do with much smaller tracts of land while biding time. It is simply difficult to tease out what the bird merely ‘preferred’ from what it truly ‘needed’ to survive.
Since the late 1940’s hundreds of Ivory-bill “reports” have come in, the vast majority being cases of mistaken identity or outright hoaxes. Still, several dozen sightings over the years bear enough credibility as not to be easily dismissable. Moreover, one must wonder how many other sightings have been made over time by people (non-birders) who didn’t have a clue what they were seeing, nor that it was worth reporting... OR, by people who knew EXACTLY what they were seeing and deliberately chose NOT to report it for fear of the dismissive judgments that would be cast their way? My guess is we would be stunned if we knew the actual number of Ivory-bill encounters that occurred in recent decades, while “experts” were cavalierly pronouncing the species extinct!
(material originally published in Chapel Hill Bird Club Bulletin 'Special Edition' 2005)
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James Tanner wrote the “definitive” study of Ivory-billed Woodpeckers in N. America in 1942 as a doctoral thesis at Cornell. His is a meticulous and wonderful study of... the half-dozen-or-so Ivory-bills he specifically observed over time at the Singer Tract in Louisiana. While he gathered information and anecdotes on Ivory-bills from throughout the Southeast, Tanner’s actual observations were retricted to a small sample of birds at a single La. location, making the generalizability of his findings and conclusions somewhat suspect. Conclusions about Ivory-bill behavior, and dietary and habitat needs are based largely upon what the birds at the Singer Tract appeared to utilize and enjoy, which is NOT NECESSARILY the same as what the species REQUIRED for survival.
As Tanner himself stated, so accurately,
“The chief difficulty of the study has been that of drawing conclusions from relatively few observations... entirely confined to a few individuals in one part of Louisiana... The conclusions drawn from them will not necessarily apply to the species as it once was nor to individuals living in other areas.”
Yet, in ensuing years these words were largely ignored as ornithologists turned Tanner’s doctoral work into gospel criteria for all Ivory-billed Woodpeckers.
At the time of his studies, Tanner concluded that fewer than 30 Ivory-bills remained in the entire Southeast scattered amongst just three states: Louisiana, Florida, and S. Carolina. In fact, some believe there may have been 200+ Ivory-bills left in the 30’s dispersed across far more locales in very small groups. Further, Tanner believed a single pair of the birds needed a minimum of 6 square miles of forest tract for survival even though the only slightly smaller-sized Pileated could reside on far less territory. Almost certainly non-breeding, juvenile Ivory-bills could make do with much smaller tracts of land while biding time. It is simply difficult to tease out what the bird merely ‘preferred’ from what it truly ‘needed’ to survive.
Since the late 1940’s hundreds of Ivory-bill “reports” have come in, the vast majority being cases of mistaken identity or outright hoaxes. Still, several dozen sightings over the years bear enough credibility as not to be easily dismissable. Moreover, one must wonder how many other sightings have been made over time by people (non-birders) who didn’t have a clue what they were seeing, nor that it was worth reporting... OR, by people who knew EXACTLY what they were seeing and deliberately chose NOT to report it for fear of the dismissive judgments that would be cast their way? My guess is we would be stunned if we knew the actual number of Ivory-bill encounters that occurred in recent decades, while “experts” were cavalierly pronouncing the species extinct!
(material originally published in Chapel Hill Bird Club Bulletin 'Special Edition' 2005)
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