1. Note that "those claiming PIWO and other woodpecker species make double-knocks" now includes Cornell (supporting link here).
2. More double-knocky background reading is available here and here.
3. Please also note this paragraph from Cornell's '05-'06 final report:
Ducks—During this past field season, we have learned that under certain circumstances duck wings can produce a double popping sound similar in timing to the double knocks of Campephilus woodpeckers. The mechanism by which ducks produce these sounds is unclear. We suspect that these pops are somehow mechanically produced by the ducks’ flapping wings, rather than being vocally produced. We hypothesize that a double knock from a nearby woodpecker would be distinguishable from a duck-generated double pop by a loud, resonant, “woody” quality. However, many of the double knocks that we have detected sound more distant and lack an unmistakable woody sound, making exclusion of ducks difficult in those cases. Based on the presence of duck vocalization and/or “wing-whirring” we have exculded 57 double-knock-like sounds from future IBWO analyses.
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Good call, Tom. It sounds like a good match; have you analyzed the interval yourself? Bet you were surprised that you had to go to CLO, whose integrity you frequently question, to find the data that no one else (am I wrong?) has provided. Do you suppose they've examined dozens of pileated woodpecker flight videos by now and will eventually retract their conclusions about flap rates? Others at BirdForum can't seem to extract flap rates from the Nolin videos equivalent to that from the Luneau video. I think you did some computations yourself.
1. Yes, I've analyzed the double-knocky interval myself. Details are in the third link in the main post above. (Note that no one can independently analyze the double-knock of an actual IBWO, since no recording exists).
2. It took Cornell a long time to admit that Pileateds do double knock (just as it took them a long time to admit that abnormal Pileateds were seen and photographed in their search area).
3. Cornell clearly should retract their conclusions about flap rates. A related post is here .
Even fangsheath had one of the Nolin birds flapping at 9.0 hertz for the first two wingbeats.
One more thing, Sidewinder. Since I view you as both a believer and a Cornell apologist, I'd sincerely like to see you specifically address just the first two issues I raised here .
One issue is the claim that the Luneau bird flies with a wingbeat frequency of 8.6 Hz for 4+ seconds; the second issue involves a right-leaning tree becoming a left-leaning tree in a critical portion of their response to Sibley.
When I've raised these specific issues with strong believers in the past, they've immmediately gone silent. Why is that?
I'm still shocked at the lack of even decent evidence. Okay, when there were a handful of pairs left in the Singer Tract Tanner et.al. went in and photographed these birds with ease. The believer side, at present, is trying to use "double knocks" to augment the remaining questionable evidence for proof that the IBWP exists?
Also, the hiatus of 60+ years without any solid evidence raises the problem of necessary predecessors for the alleged birds of today.
When I've raised these specific issues with strong believers in the past, they've immmediately gone silent. Why is that?
1. Because you can't actually see the flap rate for four seconds in the video (either breath-takingly poor observational skills or deliberate deception on Cornell's part; hopefully the former.)
2. Because with the tree lean changing directions and with the photo being cropped to match their interpretations, Cornell is simply attempting to manipulate the data to bolster their case.
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