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More Tennessee summary thoughts from Bill P. HERE.
The similarity between the Moss Island experience and that of observers elsewhere is striking. As Bill himself concludes, this "bird moves a LOT." No matter what 'hot zones' searchers establish, when they scour the area with increased people or increased searches, instead of confirming or pinpointing the bird, it seems to just move on. Very odd. Certainly during the nesting season, but even otherwise, one would expect it to have a restricted home base that it would return to every evening if not throughout the day, even while foraging might indeed take it very far afield (if it is feeding young though it must return again and again).
Or must the bird constantly move from place to place for new food resources in diminished and fragmented forest? This persistent lack of repeatability and final confirmation (very unlike other endangered species that are re-discovered) is what understandably drives skeptics nuts. No matter how many or how good the birders, or how often in the field, 'hot zones' just seem to evaporate or move on down the road. Bill attempts to surmise some parameters of the potential bird's behavior, and surmise is all we can do for now.
Again, the only solution seems to be to find an active nest site. And we've already tried human perseverance, skills, technology, and greed ($50,000 rewards ;-)) to do just that. What we seem to need is a copious dose of pure dang luck. It was certainly only luck that put Gene Sparling in a certain place at a certain moment in time to begin this whole affair, and maybe only luck can bring it to the conclusion we wish for... if such a conclusion exists.
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13 comments:
Actually many historical accounts of the Ivorybill mentioned that it was highly mobile with a very large home range. A typical quote from Chapman, "Handbook of Birds of Eastern North America" (1939) says "It does not remain long in one place, and during the day ranges over an extended territory."
The IBWO could have a huge home range, but it would likely still return throughout the day (or at least at day's end) to a more central area, whether that be a nesthole, a roosthole, or simply a central home territory. It doesn't likely just pickup and re-settle 10 mi. away every day or week or month.
But here's the even BIGGER problem with the argument: IF the bird has a huge range, there should be EVEN MORE SIGHTINGS by now!! If it was confined to a very small territory, one could argue that searchers are always on the periphery, failing to penetrate its world, and missing the bird. But if it is ROUTINELY traveling over huge distances than scattered searchers ought be even MORE LIKELY to catch glimpses, especially in the Big Woods, for example, where stakeouts have been done over wide swathes of land; not necessarily a photo achieved, but more sightings yes.
No, because if the bird returned every day to the same areas then it would be easy to relocate. If you believe that the bird has a small home range (territory is a defended area, home range is just the places the bird regularly goes) then it's extinct and all the AR, FL, etc sightings are bogus. Otherwise the bird would have been easily tracked down in the same small areas. That is also not consistent with historical reports that other than nesting pairs the bird did not frequent the same spots on a regular basis and was rather nomadic. A home range of 10-20km2 could have dozens of preferred roost trees scattered among it, the bird could use different ones on different nights. Again, I believe this is consistent with historical observations.
Mike Collins has posted an interesting clip on his website. It contains a brief glimpse of a bird in flight showing a lot of white on the trailing surfaces (dorsal and ventral) of its wings. Mike makes no claim as to the bird's identity, but notes some features of its flight. The key difficulty for me is judging the bird's distance from the camera and therefore it's size; a red-tailed hawk in the same clip provides a potential reference. I wonder what others make of the apparent size of the white-winged bird. If it is not approximately red-headed woodpecker sized, what else might it be?
Mike has now edited his entry for today with additional clips and comments; it looks very interesting..
What would the ornithologist's view on "home range" be for a single bird searching for a mate?
Not to compare ivory-bills and wolves, but there are cases of dispersing young wolves being shot or hit by a car as far as 600 miles from the nearest known wolf territory. A young animal that heads off in some direction to find a mate (or new pack) that isn't there shouldn't be expected to behave "naturally."
I agree with Bill, an ivory-bill with a small home range should be relatively easy to relocate. Observers on the "periphery" versus "interior" have little to do with recent results I think. There has been plenty of penetration into deep forests and many encounters have occurred in "peripheral" areas (indeed, it could be argued that much of Bayou DeView qualifies). The relative ease with which the white pileated was relocated is directly related to its site fidelity.
Even when nesting, the birds may be covering huge areas in today's degraded habitats. Black woodpeckers are known to routinely travel 3-4 miles between roost and nest sites. When not nesting, there is no reason for ivory-bills or even pairs of ivory-bills to confine themselves to a small area. Not to sound like a broken record, but the bird is built for distance.
Young pileateds in Arkansas have home ranges several times larger than those of established pairs. And who knows how far they may go if they abandon their established area? The radio signal will simply disappear if the bird moves too far.
Many birds, including most woodpeckers, are territorial. Considering one that may not be requires a fundamental shift in perspective.
I expect Mike Collins was feeling usurped by Bill Pulliam. Hence the new video.
Fine. Any comment about the birds in the videos?
"Many birds, including most woodpeckers, are territorial."
Does "territory" have the same meaning if a bird has no neighbors of the same species? A bird is going to have its favorite rotting trees to hang out in, but one could wander very far in search of such trees if there is no neighbor to object.
A territory is a home range that is advertised and defended. There is no necessary connection to site fidelity. An animal could exhibit high site fidelity without being territorial. However, if it doesn't exhibit such fidelity, it can't be territorial.
There is a point at which a home range will become too large to defend. The bird (or pair) simply cannot enforce its claim on such a large area. This is exactly why many animals are not territorial. If the species requires an area that is too large to defend, territoriality is not evolutionarily stable. I believe this is the case with ivory-bills (all 3 species) and has probably been the case for a very long time. Indications of sociality in the imperial (very unusual for a woodpecker) are a reflection of this I believe.
It is very possible that individual ivory-bills have established roost areas yet are not territorial. The fragmented character of today's forests may force them to move a great deal. But there are still advantages in returning to familiar spots for roosting.
spatuletail --
Whatever one might think of Mike Collins' conclusions or debate tactics, I believe his motivations have always been 100% sincere, not geared towards attention seeking. His complaints about the larger community have been that they are closed-minded, refuse to give data a fair hearing, use flawed logic, etc. Again, regardless of whether or not you agree with him on any of these points I don't think he gives a damn about who is getting their moment of "Ivorybill fame" in any given 15 minutes.
The images show something that could well be a pair of Ivorybills
Anyone else?
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