For the Birds -Report of Ivory-billed Woodpeckers in Florida
Ivory-billed Woodpeckers are back in the news again. Reports of Ivory-billed Woodpeckers (IBWO) from northwestern Florida have recently been published. However, definitive photographic or video evidence is lacking at this point.
Before discussing the details of the Florida evidence, let’s recap the history of the report of Ivory-billed Woodpeckers in Arkansas by a Cornell Laboratory of Ornithology (CLO) research team. The evidence presented in the spring of 2005 included several brief sightings by ornithologists, recordings of putative birds and a short, grainy video.
The data presented by the CLO team was met with skepticism by a number of ornithologists and birders. Reports of sighted birds without a photograph are generally not considered firm evidence. The sightings of claimed IBWO were brief. These sightings should be treated as suggestive but not definitive.
Acoustic evidence for IBWO comes in two flavors: a rapid double knock that the birds make when foraging and a characteristic “kent” note similar to the sound of a toy trumpet. Recordings of possible double knocks and kent notes were recorded on automated recorders by the CLO team. Their analysis of the sounds indicates a degree of uncertainty. No known recordings of double knocks exists, making it impossible to claim that double knocks were made by IBWO. Notes that sound like kent notes could be made by Blue Jays or White-breasted Nuthatches.
Finally, the video has been subjected to detailed analysis by the CLO team and by skeptical ornithologists. Although the CLO team vigorously defends their claim that the bird in the video is an IBWO, other analyses show that the video could be a Pileated Woodpecker. In my view, the video simply is not definitive evidence of IBWO.
The CLO team of 22 ornithologists as well as 112 short-term volunteer observers were unable to obtain photographic evidence during the 2005/2006 season. Three or four possible visual identifications identifications were reported.
Let’s stop here to acknowledge that even the most skeptical ornithologists and birders hope that the IBWO is still alive. All hope that convincing photographic or video evidence will be gathered. The skeptics will be glad to acknowledge the continued survival of the IBWO with more compelling evidence.
These differences of opinion beg the question of how the methodology of science works. The scientific method depends on trying to disprove an hypothesis, rather than confirming an hypothesis. A scientist develops an hypothesis and designs an experiment to test her hypothesis. If the experiment disproves the hypothesis, the scientist throws the hypothesis away and develops new hypotheses for her particular question. If the experiment supports the hypothesis, the scientist accepts her hypothesis as tentatively true but designs other experiments to try to knock the hypothesis down, to disprove it. A scientist begins to feel confident of her hypothesis only after a particular hypothesis has survived multiple tests to disprove it.
Scientists must be careful to avoid subconsciously supporting a pet hypothesis. One way to avoid this confirmation bias is to test two or more hypotheses at the same time. In the case of the CLO video, two hypotheses are: the bird is an IBWO and the bird is a Pileated Woodpecker. Because the video evidence in part supports each hypothesis, a scientist would revert to Occam’s razor. This useful principle simply says that when confronted with multiple possible explanations, choose the simplest one until more information is gathered. Occam’s razor favors the skeptics’ view that the woodpecker in the video is a common Pileated Woodpecker. Similarly, the kent notes could be given by IBWO, Blue Jays or White-breasted Nuthatches. Occam’s Razor tells us to reject the IBWO hypothesis on the basis of the present information.
Two weeks ago, a team of researchers based at Auburn University reported the possible presence of IBWO along the Choctawhatchee River in the panhandle of Florida. They published their evidence in an on-line ornithological journal, Avian Conservation and Ecology. You can download a copy of their paper at: http://www.ace-eco.org/vol1/iss3/art2/
The evidence consists of 14 sightings of one or two birds since May, 2005; hearing either the double knocks or kent notes of birds on 41 occasions; finding roost holes purportedly larger than those made by Pileated Woodpeckers; and finding evidence of foraging signs (neatly scaled bark from trees with tightly adhering bark). In addition, automated recorders recorded 99 possible double knocks and 210 possible kent notes. You can hear all of these recordings at: http://web2.uwindsor.ca/courses/biology/dmennill/IBWO/IBWOsounds.php
Two blogs with opposing views on the quality of the data and the plausibility of the claims for IBWO presence are Ivory Bill Skeptic (http://tomnelson.blogspot.com/) and Ivory Bills Live (http://ivorybills.blogspot.com/).
[Originally published on October 1, 2006]