The analysis by Fitzpatrick et al. of the first part of the putative Ivory-billed Woodpecker video that was obtained in Arkansas contains the following errors:

1. The first several frames of the video are presented in the "Could the white patch be the underwing of a Pileated Woodpecker?" section at this web page. A white object pops into view in one frame (33.3), comes to a stop in the next frame (50), and then disappears behind the tree again in the next frame (66.7). Fitzpatrick et al. interpreted this object to be the white patch on the dorsal side of the right wing folded against the body. The frames in the video are separated by 1/60 of a second. The white object moves approximately 3 inches between frames, which corresponds to approximately 4.6 m/s. It suddenly changes direction and then moves in the opposite direction at a similar speed, and the acceleration is on the order of 275 m/s**2, which corresponds to nearly 30 g (where g = 9.8 m/s**2 is the acceleration due to gravity). Let's compare this with the peak acceleration of the wing of a large woodpecker, which clearly accelerates many times faster than its body. An approximate model for the elevation of the tip of a wing is A*sin(omega*t), where omega = 2*pi*f and f is the flap rate. For the Pileated Woodpecker, a mean value for f is 5.2 Hz and A is about 0.3 m according to Tobalske (Auk, 1996). Plugging in these numbers, we obtain the peak acceleration A*omega**2 = 320 m/s**2, which corresponds to about 33 g. It is clear from this argument that the white object must be the underside of the right wing.



Assuming that the white object is indeed the underside of the right wing, the position of the wing and the viewing angle are similar to that of the wing in the fourth frame of the short flight in the 2006 Pearl video. A roll-over comparison of these wings is presented below. The solid horizontal line was drawn through the apparent tail position in frame 50 and used to position the tail in the image from the Pearl video. The dashed line corresponds to the edge of the tree trunk in the Arkansas video.



2. The geometry is also inconsistent with the interpretation by Fitzpatrick et al., which is presented in the "Pattern at rest" section at the same web page. It doesn't make sense to compare the specimen in B, which is seen from the side, with a bird that is perched on the back side of a tree. When I originally viewed this presentation, I assumed that the image in C was obtained by mounting the bird on the back of the tree. As the overlay below illustrates (roll the mouse over the image to view the overlay), the image in C was created by cutting and pasting part of the image of the bird in B onto the image of the tree. It is clear from basic geometry that there is a problem with this explanation; one would have much more of a ventral view of an Ivory-billed Woodpecker perched on the back of the tree, and the white patch would have a very different appearance.



3. The analysis by Fitzpatrick et al. is based in part on the assumption that the body and tail move in concert (as discussed in the "Could the white patch be the underwing of a Pileated Woodpecker?" section). Like the wings, the tail is a light object that can easily be moved rapidly. As can be seen in this video, a Pileated Woodpecker's tail doesn't necessarily move in concert with the body at takeoff. When the tail is removed from the tree in this video, it rotates nearly 90 degrees between frames while the body rotates very little.