Summary of this post: Cornell claims that the Luneau bird sustains a wingbeat frequency of 8.6 wingbeats per second for 4.5 seconds. I think the Luneau bird maintains roughly that wingbeat frequency for less than one second, then slows to more like 7.8 wingbeats per second (for a few wingbeats--maybe half a second). At this point, the bird gets so distant, blurry and obscured by trees that reliably counting wingbeats seems futile.
Background information for the above:
From Cornell's
online Luneau video analysis:
The bird in the Luneau video flies in a straight, direct “beeline” flight without changing its wingbeat frequency for 4.5 sec before disappearing among the trees.... Based on a standard video rate of 29.97 frames per second, we can calculate the wingbeat frequency of the Luneau video bird as follows: using the position where the wings are over the back forming an acute 'V' as an index point for each of eight wingbeats, we observe this position in fields 250 ("0"), 366.7 ("1"), 483.3 ("2"), 583.3 ("3"), 700 ("4"), 816.7 ("5"), 950 ("6"), 1066.7 ("7"), and 1183.5 ("8"). These eight wingbeats span 56 video fields. At 59.94 fields per second, this corresponds to 8 beats in 0.934 seconds, or a wingbeat frequency of 8.6 beats per second.
Ok, the math is pretty simple: Take 8.6 wingbeats per second and multiply that by 4.5 seconds. If we watch the Luneau video, we should see roughly 38 wingbeats before the bird disappears.
There's one problem, though: when I watch the Luneau video, I can't see much more than about
11 wingbeats before the bird is gone.
There's another problem too: evidently when
Fitz watches the video, evidently
he doesn't see much more than about 11 wingbeats. From a
Cornell story on the Cornell web site:
Presenting a plenary lecture at the American Ornithologists' Union Meeting at the University of California-Santa Barbara Aug. 25, Fitzpatrick said a new analysis of the video shows 11 wing beats of a retreating black-and-white-winged bird, consistent with the wing beats of an ivory-billed woodpecker and faster than the flight of the pileated woodpecker, commonly mistaken for the ivory-bill.
Cornell's
response to Sibley's paper says this:
The Luneau woodpecker flies with a wingbeat frequency of 8.6 Hz without undulation for more than 4 s...The close match between the Luneau woodpecker and the 1935 recording is especially important because both are faster than any wingbeat frequency ever documented for pileated woodpecker. The sustained duration of this direct flight pattern by the Luneau woodpecker is extraordinary, because pileated woodpeckers typically shift to slower, deeper wingbeats moments after launching from a perch, even when the initial few beats are rapid.
Also note that the Luneau bird's wingbeat frequency slows significantly after the initial flaps. Independent calculations (mine and another person's) show that the Luneau bird flies at about 8.5 wingbeats per second for about the first 6 wingbeats, and it slows to 7.8 or less for the next 3 wingbeats. Note that 7.8 wingbeats/second matches the wingbeat frequency of the manybirds.com Pileated.
During wingbeats 12 through 38 or so, I think it's very unlikely that the wingbeat frequency was as fast as 8.6 wingbeats per second. If Cornell is going to argue otherwise, I think they need to start by giving us a list of field numbers (as in the opening paragraph above) showing us where they claim to see all those sustained, fast, phantom wingbeats.
By the way, you can "play along at home" here. Note that the deinterlaced Luneau video plays at 59.94 fields per second. You can count the number of fields in a complete wingbeat (say 7) and then calculate an approximation for the associated wingbeat frequency. For example, about 60 fields per second divided by 7 fields would be 8.6 wingbeats per second; 60 fields per second divided by 8 fields would be 7.5 wingbeats per second).
Question: Can you count the number of fields that the Luneau bird needs to complete, say, wingbeats 25 through 35? The correct answer is "No".
Note that in Cornell's
original Science paper, they wrote this:
Two other features suggesting ivory-billed woodpecker are evident on the Luneau video, but we do not currently regard them as diagnostic, in part because we lack sufficiently comparable data for objective comparison with pileated woodpecker. First, the estimated wingspan of the fleeing woodpecker exceeds 71 cm (11), a value within the published range for ivory-billed woodpecker and at or above the maximum published wingspan of pileated woodpecker. Second, the video shows a woodpecker on a sustained escape flight that is rapid (9 wingbeats [per second]) and direct for at least 4 sec. This flight pattern matches many anecdotal descriptions of ivory-billed woodpecker (2–5) and is atypical for pileated woodpecker.
(Note: all bold font in this post is mine.)
Posts
