Monday, September 14, 2009

Why the Rush?

For some reason, a large number of people seem to be in quite a hurry to declare the Ivory-billed Woodpecker extinct. This is not a new phenomenon; it has been going on for nearly 100 years. Nor is it unique to the Ivorybill; there always are voices declaring the extinction of organisms that have not gone missing for nearly enough time to justify such a judgement. In the case of North America's three avian phantoms (Ivorybill, Bachman's Warbler, and Eskimo Curlew), it is worth keeping in mind that neither the AOU nor the US FWS has formally declared any of them to be extinct. The death proclamations are instead generally sounded by prominent individuals in the Academic and birding communities rather than the major institutions.

This leads me to wonder why. What advantages are there to decreeing a species to be extinct? I can think of several arguments that would likely be advanced if I actually posed this question face-to-face to some of the people involved. Many of these points could be grouped under "common sense." These are variations on the theme of "with it having been so long since an indisputable piece of evidence, it is just common sense that the bird is not still out there." In this view, accepting extinction is an overcoming of denial and irrational hope. However as with so many applications of "common sense" to questions that involve very large or very small numbers, statistical analyses don't support this "common sense" view, even if you reject all of the sightings, photographs, and videos since the Singer Tract birds.

I've done my own various back-of-the-envelope estimations that suggest that statistically speaking the upper limit for the global population estimate for Ivorybills remains well above zero. Actual rigorous and peer-reviewed studies have found the same thing, and have also found that it is in fact not at all impossible for a very small breeding population to persist for many decades. In a semi-humorous exercise, if I just take my own personal lifetime experience which includes zero firm Ivorybill detections, estimate the amount of time I have spent in coastal plain bottomland forests, take a reasonable value for detectability of the bird, and get an estimate of the total amount of this forest in North America, then do all the multiplication, I come up with an upper limit for the global population of something like 1000 birds. This brings up the next question: Are there 999 other people like me? This is what it would take to bring that upper bound down to 1 bird. Sure, there are 1000 other birders who might report an Ivorybill if they saw one (and many more who would not), and 1000 other people who have spent as much time in bottomland hardwoods as I have. But how many other people are there who fit both criteria? Not 1000. Birders mostly shun the swamps. Forget "common sense." The survival of the species can't be ruled out from a statistical, scientific, data-based point of view, not just at the theoretical absolutist level of the impossibility of proving the negative. It is those who declare that the species is clearly extinct who are speaking from a position of personal belief, nonrational impulse, and (dare I say) faith, not justifiable by science, data, or statistics. Most birders, even experts who should know better, vastly overestimate the efficiency of the transcontinental birding community as a bird-finding machine. The vast majority of individual North American birds live out their entire lives without ever being seen, identified, twitched, or reported by any birder. For dozens of individuals of a woodland species to go undetected decade after decade even in the eastern U.S. is in fact exceedingly easy, not virtually impossible.

Given this, why do intelligent, reasonable people still want to rush ahead and erase the Ivorybill from the roster of the world's birds? Many doubtless want to end the embarrassment of having people looking for extinct birds, fearing it makes us look like bigfoot hunters. I think this is probably what underlies the fiercely negative emotional reaction many people have to suggestions that there might still be an Ivorybill flying somewhere. But, this is based on the flawed "common sense" pro-extinction conclusion. The same applies to people who do not want public resources wasted on looking for an extinct bird. There are legitimate issues in how much, where, and how, but once again it is incorrect to base your arguments on an assumption of extinction. The whole crusade against "wasting money on an extinct bird when we have real species that need saving" is founded upon the fundamentally incorrect presumption that the Ivorybll can be reasonably known to be extinct, ergo all spending on it is wasted. Once again, even if you reject all post-Tanner evidence you still cannot safely conclude the species is gone.

With the "extinction question" being very much an open one statistically speaking, what do you gain by ditching the Ivorybill and those other phantoms? Well, you can leave three species out of your field guide, a rather miniscule savings. You don't have to spend federal money on them; although most of the time in recent decades there has not been any federal money being spent on them and it only started up recently (for a few years for one species) because of some triggering incidents. You get to leave them out of the EIS process, a "plus" of dubious value. Or perhaps you just get to feel smug and superior to all those nitwits who still cling to fairy tales (even if it is in fact your position that is scientifically unjustifiable, not theirs).

So what would have been gained if the near-universal consensus had stayed at "very rare, possibly extinct" without the loud sub-chorus of "It's extinct, stupid; any fool can see that?" Well, for one thing, birders and ornithologists would not be embarrassed about putting effort into trying to find relict populations or individuals, and would feel less need to keep their activities secret for fear of ridicule and professional retribution. These birds might have stayed on the birding radar enough that we might actually be in a better position to know now if there are indeed any left, and where. Ridicule is never a helpful activity in science; amazingly it has become almost the norm in some circles of late, usually espoused by people who believe they are defending science when they are actually hurling their jabs and taunts from a scientifically unsupportable peanut gallery.

We on the Tennessee search crew do not claim to have heard or seen an Ivory-billed Woodpecker, ever, anywhere. At Moss Island we do claim to have heard sounds that are exceedingly close to what an Ivorybill double knock might be expected to sound like, repeatedly, under circumstances that do not promote simple, ordinary explanations. Given the statistical reality that this species is quite possibly not globally extinct, and the location of the site within the generally accepted likely historical range of the species, it would be irresponsible not to follow up on this. For a wildlife biologist in the public trust with jurisdiction over non-game birds, failure to do so might even amount to professional negligence.

What can possibly be wrong in continuing to hold to a scientifically and statistically justified rational hope? And what can possibly be good about ditching this hope based on emotional, poorly thought out, unscientific "common sense?"

Other posts in this series:


At 9:31 AM, Blogger Unknown said...

I got into a disagreement with a certain field guide author on his blog on the subject of Ivory-bills. He had claimed that nobody had seen perched birds or gotten good looks at key field marks besides the white secondaries. He tried to politely say that all reports were probably mistakes, we should just admit the bird is probably extinct and go about our lives.

I corrected his assessment of the observational record by reminding him of Kulivan and Hicks, both of whom have seen perched birds at close range with field marks such as a "glowing" white bill and all-black crest. That this particular author would pat these (and other) observers on the head and tell them they made a mistake is pretty arrogant and unnecessary.

He could make his argument that we shouldn't devote resources to the Ivory-bill even under an assumption of its continued existence: if the species has persisted and its habitat is improving, it should be left alone. There are reasons to disagree with this idea, like the proposed airport next to the Choctawhatchee in Florida, but then Cornell's work seems to indicate that the encounter rate is inversely proportional to the intensity of the search. Either way, the extinction assertion can only do harm.

At 9:57 AM, Blogger Bill Pulliam said...

Joel --

The author in question has made those comments in public under his own name, so the discretion is probably not necessary.

I'll have more to say about "what it all means and where do we go from here" after I finish my tale through the 2009 season. In short, though:

Given that extinction can't be established even to a meaningful statistical confidence, I think the course of least regret is to act as though the bird exists and some of the reports may be valid. What should be done about this is debatable. The strategy of the last few years, other than the habitat acquisitions, has little to show for it. Yes the birds gotten by without us for decades, and clearly we don't even know how to find them much less conserve them. I think there is an appropriate level of federal funding in between $10,000,000/year and $0/year; it is up to agencies and their advisors to figure out what that number is, and it will vary over time depending on results or lack thereof.

Re: inverse relationship between effort and results: The hypothesis I have that explains this, IF the detections have actually been ivorybills, is simple. If the species is mobile tending towards nomadic, as historical accounts suggest. then the search effort ramps up in response to initial detections at the same time as the bird or birds are moving on to some other place. Over the years they will probably come back, but by then the search will have moved on. There has to be a name in game theory for this phenomenon.


Post a Comment

<< Home

Site Meter