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.

Other posts in this series:
First
Previous

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.

Other posts in this series:
First
Previous
Next

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."

Other posts in this series:
First
Previous
Next

The Mystery Remains

And the answer is...?

As of today (October 29, 2009), there have been no more encounters with the MIMDKWFTII. I've only made a few visits since June, and am probably done for 2009 as there's no money and not much free time in the near future. We made no real progress on the overall goal: Determine WTF the MIMDK is.

I do come away from the 2009 season, however, firmly convinced that the Mystery Double Knocker is a real and coherent phenomenon, not just an agglomeration of assorted misinterpreted and misconstrued unrelated ordinary occurences. Out of the whole 20 months I have been involved in this project, one or two minutes on one day haunt me the most. It was that afternoon of February 24, 2009, as the rain was ending and the grizzled squirrel hunter across the lake shot his supper. The string of double knocks that followed were utterly clear, perfect, and undeniable. Unlike my first encounter, I knew exactly what I was listening for, and what I was hearing. I was all alone, the rest of the crew having bailed because of the weather, sitting there by myself in the drizzly late afternoon gray. If my first encounter in 2008 was the Black Swan flying across the sun, this one was the Black Swan sitting on the hood of my truck. No denying its existence, no hope of talking myself out of this one. And, I knew the damn thing was just gonna fly off and disappear again.

As a loose end from my last post, some might wonder why I spent all this time analyzing my 3/18/09 recording when I expressed such strong objections to robobirders in an earlier post. Thing is, a real "meat birder" holding a video camera is not a robobirder. All that additional information that is lacking in robodata is present in the birder-videocam combo: context, apparent distance and direction, subjective impressions of quality, loudness, etc. The digital data and the analog experience are able to complement each other, without either making the other obsolete. But in reality, I think at this point in the Tennessee project the desire for "objective" documentation has as much to do with peer pressure than anything else. We have no doubt amongst ourselves about the reality and validity of the double knock phenomenon at Moss Island.

But what about all the alternative explanations for the double knocks? As far as the misinterpretation of ordinary sounds (e.g. gunshots, boat clunks, off-site mechanical sounds), in spite of how we sometimes seem to be viewed by northeasterners and west coast types, we are actually a pretty skilled, experienced, and discriminating crew. We take great care to rule these things out, and have clearly noted these double knocks as being something consistent and unusual. The various non-biological explanations also don't work with the spatial, seasonal, and diurnal pattern we have seen. Weather, construction, etc. aren't most active in the first three hours and last two hours of the day, they don't ramp up in late February and quiet down again around the end of March, and they don't cluster within the woods in the Rhodes-Hushpuckett Lakes corridor. No, the only thing that fits this is a biological source; specifically a mobile diurnal one. In other words, a bird.

What about duck wingtip collisions? Sorry, those may be able to confuse a robobirder, but they don't cut it as an explanation for the live sounds. They are an especially poor match for the double knocks that occur in series, repeatedly from the exact same direction; nor do they account for the freakishly intense loudness of the double knocks when heard from distances of about 200m or less. Really, there's only one option. It has to be a woodpecker -- a big one. Nothing else is properly equipped.

Here we come to the only alternative explanation that makes the cut: Could the Mystery Double Knocker be nothing more than a Pileated Woodpecker? Pileateds are certainly capable of making loud noises with their peckers; indeed they seem quite fond of this sort of thing, especially in late winter and early spring. They are also extremely common at Moss Island and in most other coastal plain bottomland forests in the southeastern U.S. However, no one has ever documented a Pileated making these dead-ringer-for-Campehilus double knocks; no one has actually documented a Pileated making any double knocks that are not embedded within an abundance of normal Pileated sounds. But, no one has yet specifically documented ANYTHING north of Mexico making these dead-ringer-for-Campephilus double knocks in about 70 years. Large woodpeckers have been glimpsed fleeing the scene of the (double knock) crime, but have not been seen well enough to definitely identify as Pileated or not-Pileated. It's not just the Moss Island Mystery Double Knocker, it's the North American Mystery Double Knocker.

But why not just claim Occam's Razor and call it a Pileated? Well, until someone actually sees something else making the sound, it can't be entirely ruled out. However, a lot of things don't fit. First, Pileateds are common and widespread in much of North America, not just the coastal plain bottomlands. Yet the phenomenally loud double knock has never been identified or described as part of their repertoire anywhere, by anyone. Perhaps it is an unusual display, used only rarely, and therefore only likely to be heard where they are especially abundant. Or, perhaps it is only a small percentage of individuals that engage in this display, which might also explain the spatial clustering in “hot zones.” Several things argue against these ideas. First, Pileateds are more common in bottomland hardwoods than in other forest habitats, but only by a factor of like 3-5, not by orders of magnitude. I live surrounded by hill-n-holler upland hardwood forests in middle Tennessee, where I see and hear Pileateds many times every day. Many other experienced birders live in similar proximity to the species. I've yet to hear any of these double knocks at home, where I spend far more time than I do at Moss Island. Even with all the publicity and skepticism surrounding double knocks in recent years, no one has turned up data showing any of these tens of thousands of backyard Pileateds making this sound. Believe me, if one of these things went off in your backyard, you WOULD notice! As for the “hot zones” being caused by individual aberrant Pileateds, they actually tend to be bigger than the typical home range of a Pileated in these densely-packed habitats, so you'd need multiple neighboring birds that posessed this aberrant behavior to explain the phenomenon this way. Anyway, woodpecker drums are pretty hard-wired, fixed, inborn display patterns. They're not subject to learning and they hardly vary between individuals or circumstances. It seems very unlikely there would be a distinctive, conspicuous, yet undescribed Pileated display still lurking out in the woods.

If I were in a court of law right now I'd probably be raked over the coals at this point for having produced nothing but circumstantial evidence. It's true, that's all I got, ain't nuthin' else. Until someone SEES the f'ing thing we will not really know. It's all Just So Stories in the meantime. I'm not going to commit the sin I have chastized others for and say “I don't know what it is, but I know it isn't a Pileated.” I don't think it is a Pileated, but I really just plain don't know what it is.

There only seem to be two options, however.

In the rest of my "wrap up" posts I'll talk about some of the larger implications of all this, speculate wildly about woodpeckers, and give opinions about what we should do from here onward.

Other posts in this series:
First
Previous
Next

Bass Notes

Singing trees, not singing fish

While I was continuing to get skunked at Moss Island, at least on the double knocker front, "Jacob" had been circulating my 3/18 double knock recording a bit amongst other interested people. I did not expect much response, as the big projects seemed to have dismissed Tennessee a year or more before. However, in June one of the Cornell PIs did have comments, and there was a bit of an e-mail conference between him and us. His initial response was two fold: very impressive double knocks, and because of the 10 second spacing almost surely just the simulations. There was some miscommunication between Cornell and Tennessee about the particulars of the simulations and timings, but even after this was sorted out the Cornellian remained convinced that mistiming, miscounting, and anomalous sound propagation were more likely than an actual response to the double knocker. He commented that, "a response pattern of just three double knocks spaced 10 s apart is unlikely for Campephilus." My observation in February of what was essentially this exact thing (three double knocks in rapid series) in response to a gunshot appeared to be given no significance. Worthy of note, we were not operating from a presumption of Ivorybillness and did not dismiss data because it did not match a priori notions of how an Ivorybill should behave. If we have Campephilus-like (actually, Campephilus-identical) double knocks at Moss Island, that fact is of great significance to the Ivorybill quest regardless of whether or not they truly are from an actual Campephilus. I'll have more to say on that in my concluding posts in this series. In the end he concluded that the sounds I recorded were "quite obviously something else than an Ivory-billed Woodpecker." My closing response to this was, "'Obvious' is a judgement. There are many rational, well-educated people who consider it obvious that the human mind was intelligently designed, that the bird in the Luneau video is a normal Pileated Woodpecker, and that double knocks are caused by duck wingtip collisions."

Beyond these immediate discussions, though, we also talked about what sorts of responses to the double knock simulator might be expected based on what has been seen in other Campephilus species. Much remains unanswered, but doesn't it seem likely that there would be wide variability between species, times of year, and local circumstances? Imagine if you tried to predict the behavior of a Lincoln's Sparrow on the wintering grounds based on the behavior of the congeneric Song Sparrow on the nesting grounds. You would get some broad generalities right, but would be wildly in error on many important particulars.

There is one well-publicized example of the behavior of a pair of Campephilus woodpeckers in response to simulated double knocks: David Attenborough's Magellanic Woodpeckers. Bear in mind, though, that this is a nature documentary, not a piece of raw scientific data. What we see in the final video is very likely a greatly edited abstraction from a large amount of footage. Who knows how many attempts were needed before this worked, if Attenborough's little tapping on the tree with two small rocks is the only attractant they actually used, whether they might have been standing 10 meters away from the birds' nest tree, if every shot is even of the same pair of woodpeckers, etc.? This is primarily entertainment, not scientific documentation. Still, though, it is the best footage of double-knocking Campephilus that I have seen anywhere.

I have wondered ever since I first shot the 3/18 video if there is a way to determine whether the double knocks I recorded are real or simulated based purely on the properties of the sounds themselves, without involving matters of timing, location, etc. To the ear the simulator can be a good approximation to the real sound, but it is not identical. Spectrographically there are some notable and consistent differences, which I alluded to in the previous post. I already posted one sonogram of the sound of the simulator at close range; here are two more along with video clips so you can hear also. As always, click the sonogram to see a larger version:

April 9:


August 21:


And here are samples of double knocks from the same simulator recorded from increasing distances, from August 21-22:


Note that to improve legibility, I boosted the gain by 100% on the middle three and by 200% on the last one, hence there is a lot more drop in loudness than it appears. The final sample, from 600m, was recorded at dawn; the others were at midday. It shows very well the greatly improved sound propagation in the dawn stillness; remember though that it is still less than 1/3rd of the distance that I was from Scott on the morning of 3/18. Looking at the whole sequence, you see the loss of the high frequencies, the blurring out of the sharpness, especially in the second knock and at midday, and the persistence of the long trailing gunshot-like echo at lower frequencies, regardless of time of day.

For comparison, here are two examples of real double knocks. First, a Powerful Woodpecker from the Macaulay Library of the Cornell Laboratory of Ornithology, catalog number 84098:


Next, here are sample double knocks from David Attenborough's Magellanic Woodpeckers (I hope the BBC, who seem to be checking my blog regularly, do not object to this use of a tiny sample of their footage. It would seem like fair use to me):


The most obvious differences are twofold:

A. The simulations have more high-frequency sound than the real double knocks.

B. The simulations show a more pronounced trailing echo than the real thing, looking almost like little gunshots with their broad rightward smear.

The real sounds are variable in their frequency distributions, especially on the low range. The examples that show the strongest base notes are the ones by the male Magellanic when he appears to be rapping close to a cavity, presumably near a void in the tree truck. This deep base is what gives some of the knocks their hollow, resonant quality.

Look more closely at the basso profundo on the Magellanic double knocks. Notice how the vertical line marking each knock bends to the right towards the bottom. There is a delay of a few milliseconds in these base tones as compared to the higher frequencies. In the Magellanic knock with the strongest base, it looks like this delay is actually greatest not in the deepest tones, but a bit above them; it's a bowing out, not a simple rightward bend. On the Powerful sonogram, the basso profundo is much less forte. But in the clearly visible faint tails at the bottom of the knocks, we see a distinct rightward bend as well.

I should say here that I am a hack when it comes to bioacoustics. Sure I have a Ph.D., but it is in Ecology, not Physics, Acoustics, or even Music. My formal training in acoustics would have been nothing beyond college physics about 28 years ago. So I am no expert here. But I'm not a total dope, either. It seems to me that this rightward bowing on the base of the sonogram, indicating a delay in the production of the tones in the frequency range of a few hundred Hz, is likely a property of the resonance of tree trunks. I expect it is this brief delay that especially gives the real knocks their sonorous, resonant quality.

Now, look back at the simulations. They do not show this feature. The initiation of the sound is at the same instant at all frequencies, making a crisp straight vertical line on the sonogram. Whatever the resonance properties of a real tree are that produce this effect, the simulator appears to lack them. Again, I'd hypothesize that the lack of this feature is what makes the simulations sound subjectively less resonant to the ear. There is no lack of the basso profundo tones in the simulated double knocks; they just happen at the exact same instant as the higher tones and thus to the ear are absorbed within the one big sharp "whack." I would propose to add a third distinguishing feature that can potentially differentiate simulations from the real thing:

C. The simulations lack the rightward bend of the sonogram at low frequencies; all frequencies of sound are produced at the same time.

As far as utility in the field, it varies between each feature. Item A, the excess of high frequencies, will fade out rapidly in a forest so it is probably of no real value. Item B, the trailing echos, certainly might be useful. In the data I posted both here and in the previous post showing the simulations at different distances, this only becomes more prominent with attenuation, as the whole sonogram dissolves into mush. Unfortunately I do not have any recordings of known real double knocks at great distance for comparison. Item C, the rightward bending base of the sonogram, might well survive over distance. As the speed of sound in air is largely independent of frequency, this feature (straight versus bent) should be preserved for as long as the sound remains crisp enough to give a good spectrographic image. It's also worth noting that this feature might be useful for separating "real" double knocks from other sounds, such as duck wingtip collisions, construction or vehicle noises, etc.

Finally, to the Tennessee sounds from March 18th one more time. Here is the clearest one, number 3 (click to enlarge):

As would be expected in either case, the high frequencies are gone. In the base tones that remain, I see rightward bowing. In fact it looks almost exactly like the shape of the Magellanic double knock at the same frequency range. There is also not a trace of the trailing echo, or any other smearing. So for the two criteria that might be meaningful in the field at a distance, this one scores as "real" on both.

Here are the other two 3/18 double knocks, along with the audio/video again:



The first knock of #1 is fairly clear; it looks bent to me. The final note of this double knock, plus both notes of double knock #2 are very faint. Still, the faint lines do seem to show a bend.

Score for this round:

Simulations: 0
Real thing: 2

Once again, this still only indicates that the sound is not the simulator and is something else rapping on wood making a sound very much like a Campephilus double knock. As always, this does not in itself prove the presence of a real Campephilus woodpecker at the site. But it again supports the idea that the Moss Island Mystery Double Knocker is a real and coherent phenomenon, not just a random assortment of ordinary sounds being misinterpreted.

Other posts in this series:
First
Previous
Next

Simulations Galore

Virtual unreality

Regardless of all the intrigue and discussion about the double knocks I recorded on March 18, the event did not have a major impact on our strategy for the rest of the season. If they were real double knocks that occurred in response to the simulator, what did this mean? It meant that the MIMDKWTFII had executed a series of double knocks in response to a loud anthropogenic banging noise in the woods between Rhodes Lake and Willow Flat. Well, that would make the third instance of a possible double knock response to a loud human sound at Moss Island, and the second one consisting of a series of double knocks within the same small area. It would make the sixth (I think; may have miscounted) occurrence overall of double knock(s) in this area. Nothing new there; just reinforcement of the previous patterns and strategies. The one thing I did feel it provided was some measure of vindication, both at the personal level and the project level, that I and we were in fact accurately distinguishing the "real" candidate double knocks from the background sounds. But the goal remained the same and remained unattained: Get a visual on the mystery double knocker, whatever it is.

It did perhaps suggest that a targeted cavity survey within this area might be worthwhile. Given the early time of the 3/18 double knocks (4 minutes before sunrise) if it was in fact a cavity roosting bird making these sounds then it might have a roost cavity nearby. Scott and Melinda were not available in the immediate future for more field work, and I was the least experienced (and skilled) cavity searcher of the crowd. I have generally considered shotgun cavity searches a waste of time and so have never really participated in them. In late March I did try my hand at it in the area from which the 3/18 double knocks seemed to have emanated. After a day I decided I was a lousy cavity searcher and dropped it, returning to the earlier approach of just sitting quietly with camera at the ready. Of course, I saw and heard nothing. Three weeks had elapsed between the last two possible MIMDKWFTII detections in the area, no reason to expect I'd get lucky any quicker this time.

In early April, Scott and Melinda were able to get back in the field. We concentrated on the same area, essentially bounded by Rhodes Lake Road on the south, a line drawn directly north from the Turnaround on the west, Willow Flat on the north and east, and the ATV trail that crosses the Rhodes Lake sill on the southeast. Melinda and I stationed ourselves variously within this area while Scott moved through it doing a double knock simulation series every hour or half hour. After Scott had to leave, Melinda and I remained an additional day and a half with me operating the simulator while she stationed herself aboard kayak in Rhodes Lake. All told we put in three days of this routine, covering April 7-9th.

After the confusion around the 3/18 event, we instituted some improvements to our field protocol for when the double knock simulator was in use. We made sure that all listeners were in radio contact with the operator of the simulator, and he would announce one minute and 10 seconds before the beginning of each series. I always turned my video camera on when each simuation began, and kept it running for about 10 minutes afterwards. When I was the operator, I made a point of getting a time stamp on the video as well. The communication, time stamping, and recording of the simulations should be adequate to resolve any future uncertainties about whether a sound was simulated or not.

As usual, however, all this cross checking and documenting was never put to the test, because none of the three of us heard, saw, or recorded anything worthy of note during this time. It did yield an abundance of recordings of simulated double knocks from various distances, however, as well as a more personal experience with how well the sound can be heard. We also got much more skilled at operating the simulator; Melinda commented that now the majority of the simulated double knocks generated by either Scott or me sounded like good approximations to the real Campephilus sound; earlier it had been a small minority. I noted that, though it was sometimes faintly audible at 1000m, most of the time the simulator was difficult or impossible to hear beyond about 500m. Leafout was under way as well, which was doubtless affecting the propagation of sound.

Here are three sets of simulated double knocks recorded from increasing distances. These are all from after we got practiced at using the device so they are much more consistent in timing, loudness, and quality than what we had going back in March. In each case I have edited the recording to place the double knocks at 1 second intervals. First, a set by me from only a few meters away (click the sonogram for the full image):


You can also see that the double knock simulator is hardly a high-tech device; it's a plywood box, open on two sides, that you tie to the tree and whack with a couple of wooden rods. Looking at the sonogram, beyond the overall loudness note the large amount of accoustic energy up in the high frequencies as well as the long trailing echos. The simulated knocks are almost like mini gunshots. Also note (this will come up later) how sharp, clean, and perfectly vertical the line is that marks the beginning of each double knock.

Next, a series by Scott from about 200m away:


Though to the ear they still sound fairly clean and doubled, the sonograms show a great deal of "mushiness." In some cases the individual knocks are not even clearly resolved from each other. Most of the higher frequency sound has faded away to near invisibility. Another feature that shows here is that in most cases (I see it best on #2, 3, and 5) the second knock is missing the lowest tones, being concentrated more in the upper part of the range of pitch that has survived the attenuation at this distance.

Finally, a set by Scott from about 500m away:


The double knocks are still audible, though the doubleness is not always so distinct. On the sonogram they are nearly gone, however. There are just faint indistinct smudges at about the right frequency; the crisp onset of the sound and the separation between the two knocks are both pretty well obliterated.

After this excursion in early April, I was mostly on my own for the rest of 2009. Melinda and Scott had other business to attend to as the nesting season approached; my own field time reduced as well. I did not use the simulator in the field much anymore. After our saturation effort in the "hot zone" yielded nothing further we decided to give it a rest. As Melinda said when she and I were packing it in after the last morning of whacking on trees, "Elvis has left the forest." Or at least he seemed to be done with his performances for the time being.

For the rest of April and in to May, I focused on spending more time in the few areas adjoining the "hot zone" where our effort had been lacking. These were places of difficult access along the northern and eastern fringes of the WMA, close to the Obion. At the very least I wanted to be sure I had seen the whole place and spent some token effort within earshot of every hectare.

Other posts in this series:
First
Previous
Next