Video Success and Failure

As promised a week or so ago, more comments about the recent Pearl River video and video in general...

To begin, an important question: Why did so many people, including some who had been quite skeptical of previous Ivorybill evidence, initially get such a pro-Ivorybill impression from Mike Collin's 11/5 video? I think several factors contributed to this. First, when the bird initially appears, it is flying towards the camera. This created a predictable foreshortening of the wings, making them appear narrower than they really are. This is straightforward enough; however, the wings also appeared pointed. This almost kite-like impression in these initial frames colored perception of everything that followed. Secondly, two related phenomena interacted to prevent most from even considering a Red-headed Woodpecker when they first watched the video. Though it was not explicitly stated, I think we generally assumed that the bird had been seen, not just videotaped. and was known to be a large bird. I believe we made an assumption that the video would not even have been circulated if this fact was not known; an unjustifiable assumption, of course. I don't think this assumption was made explicitly or likely even consciously; but it lurked there. This was compounded by the fact that the published and distributed video was a deinterlaced 60 fps video which plays at half speed on most media players. This fact was not stated when the video was first made available; I had to ask to get this piece of information through a couple of links of communication. Of course, this was not done with the intent of deceiving or misrepresenting; it was done to make the video clearer and easier to analyze. Nevertheless, most viewers' first viewing of this clip was at half speed, without their being aware of this, which caused the bird to appear larger with slower movements. If you take the clip and play it at double speed (i.e. true speed), the bird suddenly looks much smaller and far less Ivorybillish. These things combined very quickly -- long pointed wings, assumption of large bird consistent with its apparent flight style -- to put most viewers in a mental state where Red-headed Woodpecker did not even come to mind as an option. Once this impression is in the mind, you become much more forgiving of the things that appear later in the video that might point in other directions.

The lesson from this: Never make any judgement about a video such as this until you have full information about the circumstances of the encounter, what was seen in addition to what is on the tape, and all the possibly relevant technical aspects of the clip. This is in fact why I have never had anything to say about Mike's "fly-under video" from 2008; without having access to the full clip, rather than just selected segments, I feel that I have no context to judge what I might be seeing.

My second point is much more general. Birders do not seem to have figured out yet what to do with video. A video tends to be treated just as a big heap of poor-quality still images. There is a very strong tendency to pick out individual frames in isolation and just interpret what is and is not seen in them. This approach makes use of the worst parts of a video (the image resolution, or lack thereof, combined with numerous artifacts) and discards some of its most useful parts: the documentation of movement, structure, and dynamics. I've gone on at length in the past about the astonishing failures of big-name birders in misinterpreting and misunderstanding imaging artifacts in low-quality video frames; now I'd like to talk about this second aspect.

Some birders tend to speak of the "giss" of a bird as though it is a metaphysical, supernatural property; perhaps an aura that can only be sensed, not measured. This is of course ridiculous. True, "giss" is a "gestalt" phenomenon; indeed before the British term was popularized in this country in the mid 1980s, we in America called it "gestalt birding" not "giss birding." But, it is a gestalt that arises from the physical nature and behavior of the bird. The giss of a bird in flight is created by its physical structure and the dynamics and patterns of its movements. There is nothing mystically incomprehensible about it. All of these attributes such as "wingtip elevation," "wrist angulation," "flap rate," "bound duration," etc. are in fact components of gizz, crystalized and quantified. If you see a "gizz" difference between two videos, you should be able to quantify what is creating it and use this for real, scientific, non-mysterious comparisons to other videos. You can also pick up other consistent, taxon-specific attributes that might not be obvious to the naked eye, such as apparent wingtip shapes, the geometry of the wings on the upstroke, etc. This is the additional information that is available in a video that compensates for the generally lower image resolution. Failing to take advantage of this is a very bad idea. Videos should be examined as a whole, with each frame in context of the temporal sequence, and the added dimensions of time and kinetics used to their full advantage.

As a side note here, many people have mentioned that flight style is a "soft" character, subject to variation. Of course, this is true. But it is subject to variation only within limits. Birds don't learn how to flap fro scratch; that behavior is hard wired. Each species has a set range of flight styles that it can vary within. One will never find a Pileated Woodpecker flying like a Ruby-throated Hummingbird no matter how hard one might look. So, of course if you only have two examples to compare, there's little you can say. But if you have a large suite of comparison material you will get a much better sense of what the range of this "soft" character is, and can in fact determine if an unknown bird is within or outside of this range.

Finally, a point that was illustrated well by this recent video. When you do have the species identification correct, and you have suitable comparison material, you will see everything about the video in question fall in line behind this ID in short order. Allowing for minor glitches and transient illusions, every frame and every feature will be seen to be readily explained by and consistent with the hypothesis that the bird in the video is actually of species X. Once I had a suitable Red-headed Woodpecker video, the recent Pearl video immediately lined up with it so well (frame by frame and in its totallity) that it was clear there was little more to discuss.

It is interesting to note that this has never happened with the Luneau video and attempts to line it up with a Pileated. Only by misinterpreting image artifacts, ignoring flight style and wing dynamics, and focusing on select out-of-context frames can one even begin to line them up. Still, five years later, no one has yet produced a video of a Pileated in flight that even approximately matches the bowed-winged downstrokes of the Luneau bird. It took me one trip to the woods and 30 minutes to get a Red-headed Woodpecker video that was an exact match to the recent Pearl video, in plumage, structure, and movement. The contrast between these two experiences is informative.

The Great 21st Century USA Eclipse Bonanza

Nothing about woodpeckers here (thankfully)

I happened to check what might be coming up in the next few decades in solar eclipses in North America, and was extremely happy to discover that they are going to be one of the best times for USA Eclipse Watchers in all of history! The bonanza begins in less than 8 years, on August 21, 2017, with a total eclipse that transects the lower 48 from Oregon to South Carolina. My own little homestead lies just 60 miles outside of the path of totality for this event, meaning that my eclipse chase will be quite short, indeed. Favored US cities this time include Corvallis OR, Nashville, and Charleston SC. This would have been good enough news all by itself; but there's far more. Less than seven years later, on April 8, 2024, another (longer) eclipse barely catches the extreme northwest corner of Tennessee on its way from Dallas to Buffalo. I'll only be 56 and 62 years old on these two dates; so the odds are pretty good I'll get to see two total eclipses in the next 15 years within just a couple of hundred miles of home. In the last 48 years I've only managed to see two total eclipses, one of which was a 1500 mile international drive to reach.

After this, the flood continues. Before the end of the century, the moon's umbra will cross the eastern U.S. an incredible five more times! Budding young amateur astronomers who are in their teens and twenties now should count themselves unbelievably fortunate. Even us middle-aged sorts might have a shot at one or two more. On August 12, 2045 yet another totality tracks only a couple of hundred miles southwest of here; I'll be a little past my 83rd birthday then. And if I'm really lucky might be able to be on the gulf coast on March 30, 2052 for yet another encounter with the dragon at the fine age of 90.

I guess clean living is called for, huh?

Side by Side

Once I got my Red-headed Woodpecker videos from this morning processed so I could frame through them, the striking similarity between them and Mike Collins' recent bird filmed at the Pearl were so obvious that the analysis took a lot less time than I expected. So here I'll just present two side-by-side comparisons of the Collins bird and a known Red-headed Woodpecker, which should abolish all lingering doubts as to the identity of the bird. I know it did for me.

Technical info: My video was shot this morning around 9 a.m. CST at the Meriwether Lewis grave site on the Natchez Trace Parkway in Lewis County, Tennessee, about 12 miles from my house. It is the most reliable year-round spot for the species in our area, consisting of many square kilometers of lovely oak-hickory forest. My video camera is regular definition, not an HD camera like Mike's. However, I was probably considerably closer to the birds, as I was in a National Park, near a campground, and they are quite tame. I shot with manual focus at a manually set shutter speed of 1/1000s and image stabilization on; I strongly recommend all people who attempt to use consumer video cameras to document rare birds to do likewise. Fast shutter speed and no autofocus are essential for hand-held video to prevent everything from turning into hopeless blur when zoomed; use the fastest shutter speed that lighting will allow. The results are less pleasant to actually watch, having a jerky quality; but the individual frames will contain vastly more usable information. My software will only give me 30 frames per second on deinterlaced video, not 60 frames per second as Mike has. So, when I line a frame sequence up side by side between the two, I have one frame for every two of Mike's. I also avoided zooming in too far or getting too close, as I wanted the images degraded somewhat to compare better with Mike's.

Now the results:

First, a comparison of frames where the wings are fully spread during banking flight. It is these frames especially that seemed to give intriguing long pointed wings and black only near the wingtip of the Pearl River bird. These are not entirely equivalent sequences. The lighting is different; my bird is substantially less backlit and in the middle frames the white underparts are well-lit. Also, in Mike's case the bird was in powered flight and I have grabbed the frames at comparable points in successive wingbeats; my bird was engaged in a banking glide without flapping and the frames are consecutive. Still, the illustrate very well both birds in a series of similar viewing angles (click for a larger view):



The structure of the two birds is virtually identical. The shape of the white secondary patch where it is well resolved in the latter frames is also identical between the two. There does appear to be slightly less black at the wingtip of the Collins bird; however the white in the secondaries appears to end at the same spot on both birds. I suspect that the backlight has blurred out the tips of the outer primaries on the Collins bird, making the black wingtip appear somewhat reduced. I certainly see no diference at all between these two birds that suggests in any way they are not the same species.

Next, a direct frame-by-frame comparison of one full wingstroke of both. As I was able to follow the Red-headeds around as they moved actively from tree to tree, I captured their flight from a variety of angles. I have chosen the one that is imaged the most clearly from an angle most directly comparable with the Collins bird. In the case of both videos, the chosen wingbeat occurs during bounding flight, where single flaps are separated by short folded-winged ballistic bounds (I call it "cannonballing"). This is typical of flickers, Pileateds, and Red-headeds, among other species of woodpeckers, when they are covering moderate to long distances. Also in the case of both the Collins birds and the Red-headeds I photographed, the structure, dynamics, and rhythm of the individual wingbeats in bounding flight are extremely consistent. So, the two wingbeats I have chosen (one from each bird) are quite representative of their respective flight styles. I have also included a sample frame for each bird showing it in mid-bound, with wings folded, viewed from the side, to compare the silhouette of body, head, and tail (click for a larger view):



The resemblance is striking. The structure and posture of both birds at the same stage of the wingbeat is virtually identical; the timing of the wingbeats is also indistinguishable. The structure and movement of these two birds are almost exactly the same. Their folded-wing silhouettes during the bound are also essentially indistinguishable.

The bird in Mike Collins' November 5th video is, beyond all reasonable doubt, a Red-headed Woodpecker.

Dammit.

Mike Collins 11-5-2009 Video

I made it out to visit the local Red-headed Woodpecker tribe this morning and shot some deliberately mediocre video of birds in flight for comparison purposes. I'll post sample frames and side-by-side comparisons later, but it is quite clear that they are a very close match to the bird in Mike Collins' recent video. Flight style, silhouette (including apparent long pointed wings in many frames, and the shape of the head and tail), and location of white in wings are extremely similar.

In addition to posting the direct comparisons, I think there's some interesting discussion to be had here about video interpretation in general and this particular video specifically. A few of the items I'll likely get in to:

--The cognitive/perceptual phenomena that lead many people, including me, to think "Wow that looks like an Ivorybill!" on first viewing, including some who have repeatedly looked at many of Mike's other videos and said quite the opposite.

--Interpreting video is not just a matter of looking at a big heap of low-quality still images; this is a relatively new thing in the birding world and overall I don't think most birders have really begun to fully comprehend it.

--Once the correct species ID is arrived at and suitable comparison material is obtained, everything lines up very neatly and consistently.

More to come...

UPDATE: More details and comparison here.

Where Do We Go From Here?

The potato harvest is still coming up short...

After two field seasons at Moss Island, plus additional work at other sites in previous years, we Tennesseans have no more to show for our efforts than anyone else. The Federal money is drying up; State money has never been a very large pool; personal resources are of course always quite limited. The 2009 results were just enough to ensure that it will be very hard for us to simply abandon that patch of swamp and leave the situation dangling forever. But we'll mostly be working on private time and what small portion of the schedules of our full-time professional government wildlife biologists that can be allocated to this work.

For myself, I think I will concentrate just on the period from late February into March that has been the source of most of our encounters in both previous years. I'll probably just set aside a couple of weeks to be in the field full-time, and hope I get lucky. But the bigger question is, what should I actually do with my time? What have we not tried? What, of what we have tried, has "worked," at least sort of?

There are a few basic things, of course. Sitting still or paddling and walking quietly has been what has yielded nearly all the encounters. Time spent surveying structured transects, servicing equipment, or trying to "cover ground" by paddling or hiking at more normal speeds does not seem to count. And of course always being ready with the video camera; of the three instances when I heard double knocks in series, only once did I record anything and that was purely fortuitous. I think we can perhaps learn something from some techniques employed by hunters: they focus single-mindedly on their quarry, not being distracted by other tasks, and they always have their weapon at the ready. Clearly, from all the stories of near-misses, "Luneau moments," and things recorded purely by accident, Ivorybill hunters across the region have often been falling short on these measures. I've been figuring out the idiosyncrasies of my particular camera, and have learned how to keep it on standby all day without draining the battery, with 0.5 sec lead time needed to start capturing images, and with focus and shutter speed already preset.

But, of course, even if I had been on the ready like this for all of 2008 and 2009, I still have yet to actually SEE anything that I would have needed to shoot with the camera! Scott, Dave, and Allan all had only very quick encounters that would not have allowed them time to "get the bird" even with only a second or so of necessary lead time. Is there anything else we could be doing to increase the encounter probabilities?

Two other primary tricks used by hunters are attractants and geographic bottlenecks. The only attractant that has been widely used as been the simulated double knock. Even in the tropics when used with common species, its success rate has been variable and modest at best. It's nothing like what you get when, for instance, you play an Indigo Bunting song at a territorial male Indigo Bunting! Is this just a function of the behavior of the genus, or does it reflect on the inaccuracies of the sounds coming out of the double knocker as compared to the real thing? Bottlenecks have not necessarily been widely employed, and perhaps we should spend more time looking at aerial photos while thinking about a wide-ranging, obligate forest interior species. Interestingly, several riparian corridors converge on the southeastern corner of Moss Island, very close to our Rhodes Lake "hot zone."

The one final thing which has actually been effective at Moss Island is simple person power. Days when we had four or more people in the field were substantially more likely to yield something. Pulling this together with the other thoughts above, I can think of three strategies for the limited time in 2010. First, just siting in the woods east of Rhodes Lake, trying to stay awake, waiting for something to happen. Second, studying the maps further and exploring some of the surrounding areas that the riparian corridors connect to. Third, arrange a couple of weekend "big sits" to fill the "hot zone" with stationary, alert, equipped observers for a couple of days. None of this is new; but having perhaps narrowed down the season and location better it might improve the odds a small bit.

As for the grand scheme, Moss Island is just a microcosm of the larger pattern. Everyone remains in limbo, finding too much to just quit, not enough to conclude anything. If there really are Ivorybills behind any of this, there seem to be an extremely small number of them. This makes the quest simultaneously almost futile and even more important. No one knows how to proceed, and everyone seems to be shutting down or scaling back. This will mostly leave the freelancers on their own in the field, plus the occasional chance encounter, rumors from hunters, and similar things. If the beasts are still out there, they have managed this far without our direct assistance; indeed, "being found" has never really helped these birds. The Singer Tract got clearcut just the same, after all. In the Big Woods the birding community has shown a marked preference for image artifacts and incredible space-time bending white bleed over a living Ivorybill. A metaphysical sort might wonder why the critters would even bother with showing themselves to us for all the good it has ever done for them!

And now, 31 blog posts later, I'm afraid this is where I have to leave the tale. Thank you all for reading (slogging through?) to the end.

Someday, somewhere, somehow, someone has GOT to see whatever the hell it is that is making these double knocks.

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Developing Story

To divert from finishing the Moss Island tale for a moment...

Mike Collins has posted several recent videos at his Pearl River search log. One of these does seem to clearly show a large woodpecker with backlight shining brightly through its secondaries, for a couple of wingbeat cycles. Today he has posted a single frame from a new video. This frame seems to show a bird with rather long, pointed wings, almost kite-like, that seems to have light underwings with a narrow dark area at the tip. If the rest of the video makes it clear that this is actually a large woodpecker, this would indeed be exceedingly interesting.

It'll be interesting to see the rest of the video and hear the tale that goes with it, especially such things as if the bird was actually seen, not just videoed, under circumstances that confirm it was a LARGE woodpecker. That underwing pattern can be vaguely approximated by an oddly-positioned Red-headed Woodpecker, though not really very well. The black doesn't look extensive enough.

Wait and see, as always...

Update Nov. 7, 2009:

Mike has made the latest video available. Paralleling the reactions of many people, my first impression was very positive; my second impression becomes more careful. Some legitimate concerns have been voiced that I am not sure I agree with, but I do see than they need to be taken seriously. I'll not be making any public declarations about the bird in this video until after I have had a chance to go through it exhaustively and in comparison to videos of other woodpeckers of known species. When looking at a video like this, there is a tendency to pull out individual frames that tend to make one lean one way or another. But, if you have correctly identified the bird in the video, then EVERY frame in the video should be consistent and easily reconcilable with the ID you propose using uniform criteria (i.e. not invoking one set of distortions for some frames and other completely different distortions for other frames). Individual frames are most valuable in context, not in isolation. I remember that it took me months of staring at the Luneau video and extensive Pileated comparison material before I finally satisfied myself that every frame was consistent with Ivorybill and many were not consistent with Pileated. I don't think it'll take that long in this case, as the video is better quality and the things to look for are clearer to me now. But it's still not going to be done quickly.

Whatever else one might say or think about Mike Collins, he has shown perseverance in this quest far beyond almost all the rest of us.

The Global Big Picture

Larger implications

The most important part of our Tennessee experiences, in terms of wider relevance, can be summarized in one question:

What does it mean that we have perfect Campephilus-style double knocks in unremarkable second-growth forests at Moss Island?

First, a significant point about the continental-scale phenomenon. Other than a few seconds of bad video, Arkansas does not have anything more than other places. This becomes especially apparent when you allow for the vastly greater effort that has been expended in Arkansas than anywhere else. The best recent sightings have actually come from Florida, not Arkansas. The rate of "brief glimpses," "possible double knock detections" and other soft evidence per unit effort does not appear to be especially great there. So, subtract one extremely fortuitous video, and Arkansas looks pretty much the same as everywhere else.

There is a fundamental divide between the various projects on basic philosophy. The Cornell-led programs use a model that is tried and true for finding rare birds: determine habitat requirements, identify suitable habitat, and search those areas. This model is widely employed both by casual birders and scientific researchers. However, its suitability rests absolutely on the correctness of your habitat requirement information. If you make a misinterpretation there, you will be concentrating your effort in the wrong places and your search will be highly inefficient. Imagine, for example, if you searched for Bachman's Sparrows in Tennessee and Kentucky in open, mature pine woodlands, based on their habitat use in Georgia and South Carolina. You would miss the species entirely. In the northern areas they use recent clearcuts that have been scraped and burned, military live ammunition bombing ranges, and other habitats that look not one bit like the wiregrass savannahs they love so much farther south. Now, in this case, of course, we know how the habitat use varies over space and do know how to find the bird in the north or the south.

But, is this true for the Ivorybill? Do we really know how they would live in 2009 based on how they lived in 1939 or 1869? I would suggest we do not. The landscape has changed enormously during the last 100 years. Many bird species have adjusted their habitat use substantially over this interval. Is Tanner a good guide to where we should search now? Maybe, maybe not. The point is, we don't actually know.

How does this relate to Moss Island? By Cornell standards, our habitat is unsuitable. Hence, our encounters are largely dismissed out of hand. By doing so, the Cornell approach has painted themselves into a rather nasty corner. The logic is simple. To all appearances, we have Campephilus-like double knocks that are at least as good as what has been heard in the "core habitat" such as Big Woods and Congaree. If one claims that in "core habitat" these represent evidence for the possible presence of Ivorybills, but in "marginal" or "unsuitable" habitat they provide no evidence for the possible presence of Ivorybills, one has committed a logical no-no of the first magnitude. If the same sounds come from places where you have concluded that Ivorybills are not going to be, then you should conclude that these sounds have no relevance to Ivorybills anywhere. Conversely, if you feel these sounds are evidence of the possible presence of Ivorybills in South Carolina or Arkansas, then you must also accept that they would be evidence of the same in Tennessee, Illinois, Mississippi, Florida, Louisiana, and Texas. You can't have it both ways.

Anyone who seriously considers that Ivorybills might still persist, and that double knocks and other soft evidence have a relevance to indicating their possible presence, should accept that the evidence in total suggests their habitat requirements might be broader than has been assumed by Cornell et al. I'm not suggesting they will nest in fragmented second growth, or even use it as a full-time habitat; but there are ample indications that if these sort of encounters mean anything anywhere then the birds indeed are using fragmented "marginal" habitats for at least parts of their life history. These habitats are hugely more extensive than the "core" habitats, hence this possibility raises all sorts of further hypothetical possibilities for the natural history, survival, and conservation of the species, all of them positive. In the alternative philosophy to Cornell's, you search where you have learned of rumors, whispers, or credible declarations that something of interest might have been seen or heard there. This of course requires a lot of judgement, and eventually everyone will draw the line somewhere; I'd not put much stock in reports from western Kansas, for example -- although good double knocks in Nebraska or Vermont would settle a lot about what they might mean in Arkansas! But until and unless we actually find some reproducible birds and determine what their 21st Century habitat use patterns really are, minds should be kept open.

You will not get anyone involved in the Tennessee project to state that we have established the presence of an Ivory-billed Woodpecker anywhere in Tennessee as a statistical or scientific certainty. None of us has put an Ivorybill on his or her life list. However, if you asked us off the record for our own personal unscientific feelings, I think you would hear several confessions that indeed, some of us do strongly suspect that there has been at least one of these critters tormenting and taunting us in the delta woods for the last several years. Which means we also think that all that follows from this about habitat, behavior, distribution, etc. should be given serious consideration. Interconnected mosaics of fragmented second growth bottomland forest should be included within the spectrum of possible habitats for the species.

But, this is all still unproven, much like string theory and supersymmetry. The physicists need a visual on the Higgs Boson, we need a visual on the Mystery Double Knocker. Both groups have been waiting for years, and wait still. All remains in limbo in meantime.

My final post in this series next Tuesday will give my own thoughts about what might be done now, with the money drying up and the big questions still unresolved.

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The Local Big Picture

Overview of Moss Island

All told in 2008 and 2009 we had about 30 different birders spend some time at Moss Island including our crew; 14 birders put in more than two days in the field (not including the local TWRA staff who have routine buisiness on the WMA): The core crew of me, Bob, Scott, and Melinda; Dave Pereksta, Marty Piorkowski and three Cornell volunteers; Alan Mueller and four of the Cornell full-time field staff. Collectively there were nine non-controversial double knock encounters and three controversial ones, along with at least three “brief glimpse” sightings and one or two uncertain “kent” encounters. Total effort hasn't been tabulated precisely, but is probably on the order of 1000-2000 person-hours.

There is an interesting pattern I had not noticed until recently: In each case, the “lower level” encounters (glimpses and kenting) occured within a day of a double knock encounter within the same area. Scott's glimpse and possible vocalization actually occurred in immediate association with his first double knock, Dave's 2008 glimpse was the evening before and about 300m away from the controversial double knock of 3/21/08, Alan Trently's glimpse happened about 7 or 8 hours before and about 500m south of my double knock series on 2/24/09, and my kentings were heard the day before and about 700m away from the spot from which I believe the controversial 3/18/09 double knock series emanated. Yet more circumstantial and insubstantial evidence, of course, but considering that the majority of our field days yielded nothing suspicious these clusters do raise the eyebrows a bit.

Just for fun, let's assume the MIMDKWFTII actually is a real bird, and is not a Pileated. We'll assume that the double knock is its characteristic display, not an abberation. What does the pattern of our detections reveal about this critter? First, it seems clear that though it does repeatedly visit the areas around the lakes in eastern Moss Island, it is not in full time residence there. It seems very unlikely a real diurnal bird could be so hard to find unless it was just not there most of the time. So we appear to have a bird with a large home range, only a portion of which extends into the eastern parts of the WMA -- interestingly mostly within 1000m of the Obion River corridor. It might potentally use the riparian corridors, several of which come together just southeast of our “hot zone,” to move between forest fragments. The bird does seem to sometimes spend the night at Moss Island, but perhaps not in the same place each time. One double knock near sunset, and one series just before sunrise, on different dates (actually, in different years) and in different locations suggest this.

As for behavior, the bird moves a LOT. Going in the afternoon to where it was this morning, or even just a short while before, does not turn it up. It also does not seem to like to cross the lakes. Many hours have been spent on and around Rhodes Lake without the bird ever revealing itself in the open. All the encounters in the immediate vicinity of the lake have been on the east side or to the south beyond the end of the lake; the double knocks have never been heard from the west. Encounters have happened farther west, but never heard from the lake in that direction. Finally while it may be shy of the lake, it is not actually particularly worried about people. The “hot zone” is also the part of the WMA that gets the heaviest use by hunters and fishermen. That squirrel hunter was standing only 100 or 200m from it, with two fairly large dogs, and the bird did not even flee in reaction to the gunshot. No, instead it sat still and double knocked repeatedly from the same spot. Sheesh, I heard the damn thing while sitting IN MY TRUCK parked on a public road. So the difficulties in spotting this bird seem to be a function of: mobility (doesn't stay still very long), large home range (wherever you are, it is usually somewhere else), and aversion to open spaces or even edges. It doesn't actually appear to be shy or skittish, just hyperactive, fast, and stuck like glue to the forest interior.

As an interesting note... most of these features were (are?) evidently typical behavior for an Ivory-billed Woodpecker -- more insubstantial circumstantial evidence. The one exception is the apparent utilization of fragmented forest habitat connected by narrow corridors of several miles in length. As I have written before, if Ivorybills never learned this trick, then there is no way they survived the 20th Century. So regardless of whether this was characteristic of 19th Century Ivorybills, it must be typical for 21st Century Ivorybills or there will not be any of them to look for.

Now for a bit more about the double-knocking behavior of the Mystery Double Knocker. As I mentioned before, its knocking is concentrated in the first three hours and the last two hours of daylight, and from late February until very early April. Given what appears to be the large home range and high mobility, it is hard to actually know if it really only double knocks infrequently, or if it just moves so much between performances that any given observer will not hear it more than once a day. On the one occasion when we had 12-18 people on site for two days, there were three possible encounters, two of them from different locales separated about 500m and 65 minutes. This might argue more for the problem being that the creature is alway on the move rather than its being unnaturally quiet. It does at times appear to react to loud banging sounds by double knocking; as it did this both in response to a gunshot and the double knock simulator it raises the question of whether the apparent "response" to the simulator might in fact just be a non-specific "reaction" to a general loud noise not actually recognized as a "double knock." We might do just as well by simply shooting a .22 at the top of every hour.

Perhaps to contradict myself where I stated that the hypothetical bird is usually not at Moss Island, I can play some numbers games to make guesses as to what fraction of its time it does spend there. First, working in orders of magnitude, we had a "detection" about every 100 hours. Using a general rule of thumb I find useful for many landbirds, 1 detection per hour corresponds roughly to 10 birds per square kilometer. So this detection rate would mean 1 bird per 10 km², and since we are not hypothesizing more than 1 bird this would suggest a 10 km² home range for this critter. Our "hot zone" covers about 2 km², so this gives us a very very rough estimate that the bird would be in the hot zone about 20% of the time. Where is it the other 80%? Who knows? It's still only a hypothetical bird anyway. Just to be intriguing, the hot zone covers about 20% of the forests at Moss Island, so it conceivably *could* be a full-time resident there and the apparent hot zone could still be just a statistical fluke. Or it might spend 80% of its time farther north or south along the Obion - Forked Deer riparian complex, where there are other sizable forest fragments within a few miles.

Something that might argue for a larger percentage of time spent in the hot zone is this simple observation that I had overlooked before: On days when we had 4 or more people in the field, we had a possible detection more than half the time. And again, over the two days when we had 12-18 people in the field, we totaled three possible detections. That pattern might suggest that in fact the hypothetical bird is in the hot zone full-time, or at least visits the hot zone for a while on most days. This scenario would require the bird to be significantly quieter than the average woodland bird to explain the low detection rate per observer.

These are all just games with numbers, patterns, and ideas. We of course do not have any direct evidence as to the identity of our Mystery Double Knocker. None of our sightings are remotely close to "good," and no one anywhere in North America has yet actually identified the source of these double knocks. No quantity of circumstantial patterns, hypothetical scenarios, deduction and inference can ever make an Ivory-billed Woodpecker out of mere noises and glimpses. Whatever our own personal suspicions and hopes might be, we understand perfectly well that we have not "gotten the bird."

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