On September 28, 2009, I submitted a manuscript on “Cruising flight of the Ivory-billed Woodpecker (Campephilus principalis)” to the Proceedings of the National Academy of Sciences along with these figures and movies. The paper was rejected on the basis of these comments by the editor and reviewers, which focus on irrelevant points and contain serious errors but fail to expose any flaws in the analysis.

The editor makes the hyperbolic claim that “extraordinary claims require extraordinary evidence.” Two independent groups of ornithologists have recently published evidence for Ivory-billed Woodpeckers, and there’s really nothing extraordinary about the acquisition of additional evidence by another scientist. It’s hard to understand the claim that the manuscript “does not develop ‘scientific’ aspects of avian flight in the context of the IBW identity controversy.” The video reveals that the flap style is dramatically different from the expected duck-like flaps. This is exciting new information about a topic of great interest in American science, and it’s useful in the context of identifying this species. The first data on the flap rate and flight speed in cruising flight are also interesting from the perspectives of science and identification. The editor mentions a lack of “good data on the flight characteristics of the IBW.” The video actually provides the only such data that exists, and it’s good data despite being out of focus — the flap rate, flight speed, and wingtip curves are all well resolved. The editor claims that there is a lack of information on “the range of characteristics for the pileated woodpecker,” but good flap rate and flight speed data have in fact been published for this common species. It would be interesting to see data on other large woodpeckers, but other Campephilus species are irrelevant to the identification issue since none has ever been recorded north of Mexico.

Reviewer 1 claims that the “quantity and quality of these video data are insufficient.” Insufficient for what? The video provides reliable information on the wingspan and flap style that rules out all but two species (one of which is easily ruled out). The reviewer claims that a sample size of one isn’t conclusive, but generating statistics is not an objective of the manuscript. The video shows a large (in terms of wingspan) bird in cruising flight that has the distinctive flap style of a large woodpecker; this sample of size one shows the wings folding closed in the middle of each upstroke and suffices to rule out most large birds. The flap rate of the bird in the video is ten standard deviations greater than the mean flap rate of the only other large woodpecker that has ever been documented north of Mexico; this sample of size one shows many flaps in cruising flight and suffices to rule out Pileated Woodpecker. The reviewer tries to explain away the fact that the flap rate and flight speed are inconsistent with Pileated Woodpecker by making the wild speculation that the frame rate was erroneously changed by a factor of two. The original digital video tape is available for inspection to anyone who wishes to verify that there was no such error. The reviewer comments on “dorsal white stripes in several video frames.” Dorsal stripes were observed in the field, but they weren’t claimed to be visible in the video; prominent white patches consistent with Ivory-billed Woodpecker are visible on the wings. The reviewer suggests that white markings “could potentially derive from solar specular reflection,” but this is not possible since the bird was to the northwest of the camera before 9:00 on an overcast morning. The reviewer claims that white markings “could also be attributed to a partially leucistic Pileated Woodpecker,” but every characteristic of the bird in the video must be taken into account when considering each candidate species; Pileated Woodpecker is easily ruled out for several reasons other than the markings, including flap rate, flight speed, and wing shape. The reviewer claims that there’s an issue of “low temporal resolution of the camera,” but the temporal resolution of 60 Hz was sufficient for an expert on woodpecker flight mechanics to produce detailed wingtip curves from the video, and it’s clear at this temporal sampling that the bird has the distinctive flap style of a large woodpecker. The reviewer incorrectly speculates that the Ivory-billed Woodpecker should have a lower flap rate than the Pileated Woodpecker. Tanner reported that the Ivory-billed Woodpecker has a high flap rate, and this would only make sense if he was tacitly comparing with Pileated Woodpecker (the only comparable species that occurs north of Mexico). I have gone far beyond the speculations of the reviewer and found that both of the leading flap rate models predict that the Ivory-billed Woodpecker has a significantly higher flap rate than the Pileated Woodpecker. These results are interesting but inessential since Tanner’s account trumps model predictions. I decided not to include this material in the manuscript in order to force the reviewers to focus on the video.

Reviewer 2 mentioned that all images of ivorybills seem to be blurred, but the analysis is mainly based on quantitative aspects of the data that don’t require sharp images, including the wingtip curves, flap rate, flight speed, wing aspect ratio, and wingspan. The reviewer mentions being confused that I have had several sightings but don’t use a digital camera with a powerful lens. Such cameras have been tried without success, and it’s not difficult to understand the reasons. Other than a brief flurry of activity in February 2006, my sightings have been very sporadic. It’s difficult to search for an extremely rare and wary bird in a vast and remote swamp and keep a camera (especially one that’s big and expensive) ready at all times for encounters that typically occur months apart and last for a few seconds. One strategy is to record continuously with a video camera, as I was doing when the birds in the 2007 and 2008 videos were detected. The reviewer suggested applying Pennycuick’s model, which I have already done as discussed above.