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An editorial in Avian Conservation and Ecology explains the decision of the editors to publish the paper by Hill et al. despite the lack of definitive evidence. They acknowledge the controversy around the question of whether ivory-billed woodpeckers persist, but argue that they have a responsibility to further an ongoing discussion.
What is that responsibility, more specifically? Consider the scientific method: observations about nature generate hypotheses and predictions that are subjected to further scrutiny. This leads, through strong inference (Platt 1964, Chamberlin 1965), either to falsification of the hypotheses, or an increase in our confidence that the hypotheses can account for the observations. In this case, the null hypothesis seems clear: Ivory-billed Woodpeckers are not present—in Arkansas, Florida, or anywhere else for that matter. Some advocates may treat the alternative hypothesis—that Ivory-billed Woodpeckers are present, at least somewhere—as an article of faith, and skeptics will rightly point out that the evidence for this alternative hypothesis may be weak. From a scientific perspective, it seems safe to state that the observations do not allow rejection of the alternative hypothesis out of hand. Regardless, as Carl Sagan pointed out, absence of evidence is not evidence of absence. Hill et al. conclude that their evidence at least warrants an expanded search in space and time. We agree. “Harder” physical evidence, such as photographs, would enable an unequivocal rejection of the null hypothesis. If no such evidence ever materializes, despite an expanded search effort, the alternative hypothesis is assessed just the same. Furthermore, Hill et al. offer new forms of evidence (cavity size distributions, putative foraging sites) that can be assessed in other areas, including those in which Ivory-billed Woodpeckers clearly are absent. Thus, they provide both evidence consistent with the alternative hypothesis, and means to increase confidence in our inability to reject the null hypothesis. Science is a way of knowing, and knowing occurs either way.
