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Note: Google's Blogger platform was down for 48+ hours (making the posting of new blogposts or comments un-doable), but appears to be working once again....
Generally speaking throughout the avian kingdom, larger birds have slower wingbeat frequencies than their smaller cousins. Louis Bevier's original 2007 analysis for PIWO vs. IBWO wingbeat frequency follows in that vein, for any who haven't seen it:
http://web.mac.com/lrbevier/ivorybilled/Wingbeat.html
There is NO firm data for what the range of wingbeat frequency for the Ivory-billed Woodpecker should be. None, just speculative conjecture. The one specific piece of old Singer Tract audio (of a bird flapping) that is sometimes alluded to for analysis is useless and meaningless, with no accompanying video to know WHAT is even doing the flapping --- but even presuming it is an Ivory-billed Woodpecker it is at least as likely that the bird is merely flapping to maintain balance on a tree, or fending off an intruder/interloper, than a recording of actual flight (though it may be 'hopping' from one branch to a nearby one). This specific area of analysis is fraught with problems and assumptions (and uncontrolled variables), but I believe Bevier's analysis, in this instance, is as good as is out there. Thusly, for now, I'm more interested in video clips of purported IBWOs that show birds flying below or at the low end of the purported range for PIWO wingbeat frequency (which also is not well-established).
But short of a truly definitive photo or video (requiring no analysis, beyond proof of authenticity), what I'd really like to see at this point are more high quality and lengthy sightings that come from multiple experienced, credible observers (lone observer claims simply are not taken seriously by most of the birding establishment at this point), and preferably, then, repeated by others (photos, video can come later, if at all).
So far, it ain't happenin' :-(
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1 comment:
If there are no firm data on what the wingbeat rate should be for an ivory-bill, then surely the extrapolation of trends, cited by Bevier and Sibley on more than one occasion, is worse than useless, it is downright misleading. The variation about the regression line is tremendous, so much so that the flicker averages a much higher wingbeat rate than the smaller Lewis's woodpecker. The hairy seems to have virtually the same rate as the much smaller downy. Instead of acknowledging the high aspect ratio of the ivory-bill wing, the historical descriptions of "duck-like" flight, and the Singer Tract audio, all of which give us every reason to think the ivory-bill may average a much higher wingbeat rate than the pileated, Bevier chooses to focus on a simple trend, blatant exceptions to which are staring us in the face.
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