Tim Allwood said:
I haven't seen the full Collins footage, just the still, but no one of any standing thinks it's of an IBWO
If that's true, then let's hear them make their case. The video has been available for everyone to see for several months. So far, nobody has made even a remotely convincing argument that it's a pileated. There is no shortage of people who would love to shoot down that video, but nobody has done it. Why not? A detailed discussion of several aspects of the video (along with still frames and video clips) is given at
fishcrow.com. Here are the key points:
* The neck-head-crest-bill profile. The profile of a pileated is quite different from the profile of an ivorybill. A pileated has a much shorter and stouter neck. The way the bill is attached to the head of a pileated is very different (like a Neanderthal, they have no chin). The head shape is also very different. The bird appears in focus in the video, and the profile is well resolved. In fact, the bill is even resolved. I have posted a Powerpoint presentation at fishcrow.com that shows that the profile of the bird in the video fits the profile of an ivorybill specimen like a hand in a glove. It also shows that the profile of a pileated doesn't fit the profile of an ivorybill. In my opinion, this aspect of the video alone is conclusive proof that the bird is an ivorybill, but there's much more.
* The left dorsal stripe is clearly and unambiguously resolved in the video. Pileateds don't have this field mark. The only question is whether the feature is actually a field mark, something else such as vegetation, or an artifact. By comparing with an ivorybill specimen that was photographed from the same angle, it is clear that this feature appears in precisely the right location on the bird. In fact, there is even a thin dark strip to the right of the dorsal stripe in the images of the specimen and the bird in the video. Is it vegetation? There is a stripe to the left of the dorsal stripe feature that is vegetation. Less than a second before that frame in the video, the bird was rotated out of view. At that time, the position where the dorsal stripe feature later appears is up against the sky, and it is clear that there is no vegetation in that position. Is it an artifact? Appearing in that image are various features, such as twigs, that are of comparable size to and smaller than the dorsal stripe feature. By comparing with the still photo (which has higher resolution), it is easy to see that these features are well resolved in the video. So it is clear that the dorsal stripe is not an artifact.
* Trailing edge of the right wing. The camera was partially zoomed out when the bird flew to the right, but there are enough pixels to resolve a light colored feature exactly where it should appear on the trailing edge of the top of the right wing. In that frame, the head of the bird is obscured by vegetation, but there is no vegetation blocking the wing. Everything about the wings appears to be correct in that image. The tip of the left wing appears to be visible below the lower edge of the right wing. If the trailing edge feature were an artifact, one would not expect to see such logical order in the image. It is extremely unlikely that an artifact would perfectly mimic such details just by chance.
* Behavior. When perched, the bird assumes the classic leaned back posture of an ivorybill. Although this alone is not conclusive evidence (pileateds sometimes assume such a posture), the bird in the video assumes this posture the entire time it's in view--even when moving. The bird rotates around the branch like a door on a hinge while remaining in the leaned back posture. Then it hitches up the branch with an unusual "slithering" motion.
* Wing length and shape. The wings are long, thin, and pointed like an ivorybill's wings but unlike a pileated's wings.
* Flap style. The flapping leap across the fork of the tree is totally unlike the way pileateds move between nearby branches. The flaps are very deep, which is what you would expect for a heavy bird with relatively long and thin wings. In fact, this is what Tanner states on p. 58: "In the initial flight, when the wings are beaten particularly hard..." When the bird flies a longer distance to the left in level flight, it doesn't tuck its wings between flaps like pileateds.
* Flap rate. There are approximately 7.5 flaps per second when the bird flies to the left in level flight. According to a paper by Tobalske, 7.5 is the highest observed flap rate for pileateds, but we need more than just an upper bound. This important problem needs to be revisited. A large data set will be required to determine the distribution of flap rates under different conditions. How often does a pileated in level flight achieve a flap rate approaching 7.5? I suspect it's very rare based on more than three months of intensive observations of pileateds in the Pearl. I took a small data set (videos of pileateds in level flight) and never observed a flap rate greater than 4.4. If pileateds in level flight approach a flap rate of 7.5 with any amount of regularity, then one should frequently observe flap rates greater than 5 or 6.
* Observations. I saw an ivorybill fly over to the area where the bird was captured on video minutes earlier. I had sightings and heard kents in the same area several times that week. Since 1999, there have been several ivorybill reports within a few miles of that area.
