Wednesday, September 07, 2005

Wing beat rate in the Luneau video

Here is an interesting, fairly new article from Cornell's web site.

A snippet from the above article:
While skeptical ornithologists recently claimed that the video images, captured in the Big Woods of eastern Arkansas in 2004, likely show the smaller but similarly patterned pileated woodpecker, new studies indicate that the pileated woodpecker beats its wings between 7 to 7.5 times per second in a slow rowing motion.

By comparison, the bird in the video flies at a rate of 8.7 beats per second in a direct duck-like flight consistent with historical accounts of ivory-bills. Fitzpatrick played an April 1935 audio recording, made by the Lab of Ornithology's founder Arthur Allen, of an ivory-billed woodpecker in the Singer Tract in Louisiana flying away from its nest hole. The flapping wings are clearly audible. Using a spectogram showing audio patterns over time on a graph, Fitzpatrick showed that the 1935 ivory-bill had flapped its wings at 8.6 beats per second.

"My personal view is that I am convinced there are ivory-bills out there, one or more," Fitzpatrick said. "Absolutely convinced."
In my personal opinion, this "wing beat" argument constitutes "grasping at straws". For one thing, the bird in the video does not fly directly away--it is weaving back and forth through the trees (this weaving is easier to see at full speed in the Luneau DVD than it is in slow motion in the online video).

For another thing, the difference between 7.5 flaps per second and 8.7 flaps per second is not large. I see no reason that a Pileated, weaving in initial escape flight through the trees, couldn't fly at 8.7 flaps/second.