End of the road, finally, for Ivory-billed Woodpecker?
by Nate Swick
From Birdwatching magazine's Field of View blog, comes a fascinating recap of two recent studies using statistical analysis to evaluate the probability of finding living Ivory-billed Woodpeckers in the 21st Century, perhaps putting, if not the final, then one of the very last nails in the coffin of maybe the most polarizing and puzzling ornithological story of the last several decades.
The two independent studies, from the University of Vermont and Woods Hole Oceanographic Institute, use different methodologies but come to similar conclusions; that for Ivory-billed Woodpeckers to persist into the early 21st Century, the populations would have had to be significantly larger than James Tanner's estimates in his seminal 1930s study.
The papers are remarkable in that both took a much closer look at uncertain sightings, with the Woods Hole group treating them formally for the first time.
“It is easy enough for skeptics to pick apart a single statistical analysis,” [lead author of the University of Vermont study Nicholas Gotelli] says. “Statistical analysis of non-experimental data is, after all, an indirect form of inference, and the results always depend on the assumptions of the model and the kind of data that are used. But in this case, you have two independent teams that are using different data sets (for the historical analysis, we excluded everything except for valid, dated, geo-referenced specimens, whereas [Woods Hole investigator Andrew] Solow's analysis included other kinds of observations, such as photographs) and completely different statistical models, but they arrive at the same qualitative conclusion (persistence is improbable). These analyses are also consistent with earlier statistical studies published by Chris Elphick, Dave Roberts, and other colleagues. Taken collectively, the results of these multiple independent investigations make a powerful case that the Ivory-billed Woodpecker is extinct.”
The entire post, including links to the paper abstracts and responses from Ivory-bill experts Jerry Jackson and Bobby Harrison, is well worth a bit of time.