Scrambled

This is your brain on Ivorybills

On my return home on March 12, the first order of business was to flesh out my "official" account of the Bambam Incident before I read or listened to anything else. I had scribbled some quickies in the field at the time, and written up the incident in my field notebook at greater length later that same day, so it was mostly a matter of adding grammar, punctuation, context, locations, etc. I won't reproduce the writeup verbatim here, as it has been pretty thoroughly paraphrased and quoted in my previous post.

With that out of the way, I felt free to start listening to recordings and reading historical accounts. In terms of quality, rhythm, etc., recorded double knocks of Pale-billed Woodpeckers were awfully freekin' close to what I heard, if one were to put them through a massive mega amplifier. Contemporary descriptions by early 20th Century observers of Ivorybill double knocks were also sometimes uncannily accurate descriptions of the sounds from my 21st Century encounter. Loud, very loud, unexpectedly loud, everyone stressed this. I had a spine-chilling, we're-not-in-Kansas-anymore moment when I read this quote from Don Eckleberry, describing an encounter with a female Ivorybill in Louisiana:

With a few disordered feathers properly and vigorously rearranged, she gave her distinctive double rap, the second blow following so closely on the first that it was almost like an echo--an astonishingly loud, hollow, drumlike Bam-am!

In my own writeup I had describe the loudness of what I heard as "astounding" rather than "astonishing," and I had used a "b" where he used a hyphen in the onomatopoetic spelling of the sound. Other than that...

But what to make of this? Obviously some banging sounds in the woods do not an Ivory-billed Woodpecker make. We were not in any position to make any firm declaration about what the source of these noises was. But we could ponder, speculate, and infer. One thing seemed clear: the source of the noises was biological. They were heard in calm and near-calm winds, repeatedly within the same general area but not at the exact same spot, and they seemed to all be nearly identical. What else is going to do this but a mobile biological source? But.. WHAT biological source? The one critter that has been documented making a very similar sound is (at best) one of the rarest organisms on the continent, and this scraggly forest is hardly the right habitat for it.

Hold on, let's revisit that last statement. Do we really know what habitats a relict surviving Ivorybill would be using now in this century? This has of course been the subject of much debate. We have a modest amount of information about 19th and early 20th Century habitat usage; and that actually points to a moderate amount of plasticity: bottomlands, pines, virgin growth, cutover stands. But even if the species was restricted to old-growth bottomland hardwoods 70 years ago, are there strong reasons to conclude that any possible surviving birds would still be restricted to this habitat or its close approximations? Well, actually, no.

Many forest birds have modified their habitat usage in recent decades and centuries. Chimney Swifts are an obvious example; also quite telling is the Vaux's Swift which has only begun moving out of old growth and into chimneys in the last few decades. But of more direct relevance, consider the following quotes:

When found they are usually in regions of original forest growth, rarely being seen where the woods have been once cut over. [...] As this Woodpecker seems not to possess the faculty of adapting itself to the new conditions created by civilization, it is quite possible that it will not long survive the passing of our primeval forests. T. Gilbert Pearson, Birds of America, 1936.

Its presence in a region is more often revealed by the large cavities it excavates in dead stumps and trunks than by actual observation of the bird itself. [...] This species is common only in the wilder parts of its range. Frank M. Chapman, Handbook of Birds of Eastern North America, 1939.

Both of these early 20th Century characterizations are of the habitat requirements of the Pileated Woodpecker. In fact, as we all know, over the intervening decades Pileateds managed to adapt to forest fragmentation and second growth quite well, thank you, and are now widespread in habitats well beyond the range of what was described in the 1930s.

There's also another fundamental, perhaps somewhat tautological factor at work. If in fact Ivorybills were an obligate old-growth bird, then yes, they are now extinct. If they were never able to utilize second growth and fragmented forest, then there is absolutely no reason to be looking for them now anywhere. But even given the historical accounts of their habits they demonstrated a bit more flexibility than this; and given the actual history of Pileateds and various other forest birds since the industrial revolution, it seems brash and unjustified to presume that the habitat utilization of a 21st Century Ivorybill would be the same as that of one in the 19th Century.

All these intellectual ponderings are fascinating and intriguing, but more urgently we were in something of a campephilitic frenzy. On March 13th Bob heard another double knock near Forked Lake, another oxbow lake situated midway between Hushpucket and Rhodes Lakes. As an interesting linguistic side note, "Forked" in place names in this area is pronounced with two syllables, King James style. We all felt we had to strike while the zone was hot and before the leaves closed the canopy in and cut off sight lines. Rapid response took priority over full analysis of what we had; there'd be much more time for debate and discussion later. Scott was making arrangements for a mass invasion, an effort to get as many people as practical out in the WMA at the same time for a couple of days. Cornell was offering the loan of their Arkansas volunteer crew for a few days. TWRA, the Feds, and selected invited guests were set to rendezvous at Moss Island on March 20-21.

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