Ivory-billed Woodpecker (formerly updates) (29 Viewers)

pianoman said:

Ortolan is probably right that the Bayes approach is most appropriate when determining if an IBWO sighting is genuine. But to do that you need the following:

(A) The prevalence of IBWO as compared to other large woopecker-like birds.
Bittern's point about visibility could be factored into this figure.

(B) The proportion of sightings by the observer of large woodpecker-like birds incorrectly identified in the past as NOT IBWO.

(C) The proportion of sightings by the observer of large woodpecker-like birds incorrectly identified in the past as IBWO.

True, Bayes considers the sensitivity of a test rather than the competence 1of an observer. This complicates things, because a test is deemed to be the same for all the data gathered, whereas observers' competence may vary.

In any case, we don't know (A) because that's what we're trying to find out!

We don't know (B) because we don't have stats on unremarkable sightings of PIWO or other birds.

And we definitely don't know (C)!

So I'd say the stats approach may be a non-runner!

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The testing protocol is the same but since different people respond in a different way to the test (our biochemistry may be surprisingly different when looking into the finer details) the test is not the same and thus, there is no conceptual difference between the sensitivity of a test and the competence of birders.
B) and c) Agreed, but aren´t these the most interesting points? Brave people might step forward and throw in their own estimates of their identification skills in this hypothetical situation. I would think every birder has some gut instinct about his/her skills. Upthread there were numerous claims about being confident in identification, since the two birds are very different.
Truly, stochastic calculations cannot prove the existence of the bird. Nevertheless, I feel it is quite helpful to have a scientifically based rule of how to take advantage of knowing the prevalence of a species for an otherwise not 100% certain identification. "Extraordinary claims require extraordinary proof. " Bayesian calculations do nothing but quantify the degree of extraordinarity required for proof.

you couldn't make this stuff up, could you?

well, apart from the sightings...

Tim

can anyone give me the probablility the bird is extant. Or the probablility Lunueau is an IBWO. I mean 10.7% wasn't serious, was it? I'd love to see it.

Fair point on the test sensitivity, Ortolan.

And yes, you could plug in guesses or "what ifs" for the variables and see how the sighting results come out.

Only a bit of fun Tim; to get your answer you'll have to come up with your proposed values for A, B and C and then ask Ortolan to do the maths for you.

Actually in your case it's easy -
A = 0 so probability = 0!

Anything else, I'm not sure about.

I'm going to get the heck out of this thread now...

Tim Allwood said:

you couldn't make this stuff up, could you?

well, apart from the sightings...

Tim

can anyone give me the probablility the bird is extant. Or the probablility Lunueau is an IBWO. I mean 10.7% wasn't serious, was it? I'd love to see it.

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Ok Tim I´m willing to calculate the probability that the bird in the L video is an IBWO. They should have done this in the science article. But I would need your honest cooperation to come up with a number. I warn you, this might not be easy. I think, we can agree that there are only two possibilities, IBWO or PIWO. Here it goes:
1) Imagine, 1000 years ago and you are in these swamps. In other words, please forget about any prevalence, extinct, extant, whatsoever in your considerations. Just try to assume that it is equally well possible to see an IBWO or a PIWO at this particular place. This is absolutely necessary because the probability calculations take care of the abundance issue separately from the likelihood of proper identification based on the presence or absence of identification marks.
2) Now, your friend tells you he has seen for certain an IBWO right at the L place. He has got extended views, without doubt it was an IBWO. You are eager to find the IBWO, but all you get upon arrival at the place is a glimpse like in the video. How confident would you be, based on your own identification skills together with the rather limited view, that the bird was indeed an IBWO? Your decision should not be biased by the view your friend had. You perfectly know, regardless of the observation your friend had, a PIWO is equally likely at the L place. Provide a percent value, 0%, 10%, 80% ....! Would you put it on your list as an IBWO?
3) Next year, your friend told you, that there is for certain an PIWO at this place. Same situation. same video. How confident would you be, based on your own identification skills based on the rather limited view, that the bird was not a PIWO but an IBWO? PLease, do not let enter any abundance or likelihood consideration into your reasoning. Provide the percentage based solely on what you have seen!

This may seem fun, BUT the likelihood of an identification being a particular species can be estimated on the basis of field marks seen, general impression etc., skill of observer independent on the probability of seeing the bird at a particular place. Based on abundance of the bird this will provide a number for the likelihood of the bird indeed being the species as identified. The current practice of assessment of observations, in contrast, has only accepted, rejected, not clear. What about "stochastic birding" introducing probability considerations into identification? This would be truly something one can work with. Now, many observations are just out of the play.

ortolan10 said:

Ok Tim I´m willing to calculate the probability that the bird in the L video is an IBWO. They should have done this in the science article. But I would need your honest cooperation to come up with a number. I warn you, this might not be easy. I think, we can agree that there are only two possibilities, IBWO or PIWO. Here it goes:
1) Imagine, 1000 years ago and you are in these swamps. In other words, please forget about any prevalence, extinct, extant, whatsoever in your considerations. Just try to assume that it is equally well possible to see an IBWO or a PIWO at this particular place. This is absolutely necessary because the probability calculations take care of the abundance issue separately from the likelihood of proper identification based on the presence or absence of identification marks.
2) Now, your friend tells you he has seen for certain an IBWO right at the L place. He has got extended views, without doubt it was an IBWO. You are eager to find the IBWO, but all you get upon arrival at the place is a glimpse like in the video. How confident would you be, based on your own identification skills together with the rather limited view, that the bird was indeed an IBWO? Your decision should not be biased by the view your friend had. You perfectly know, regardless of the observation your friend had, a PIWO is equally likely at the L place. Provide a percent value, 0%, 10%, 80% ....! Would you put it on your list as an IBWO?
3) Next year, your friend told you, that there is for certain an PIWO at this place. Same situation. same video. How confident would you be, based on your own identification skills based on the rather limited view, that the bird was not a PIWO but an IBWO? PLease, do not let enter any abundance or likelihood consideration into your reasoning. Provide the percentage based solely on what you have seen!

This may seem fun, BUT the likelihood of an identification being a particular species can be estimated on the basis of field marks seen, general impression etc., skill of observer independent on the probability of seeing the bird at a particular place. Based on abundance of the bird this will provide a number for the likelihood of the bird indeed being the species as identified. The current practice of assessment of observations, in contrast, has only accepted, rejected, not clear. What about "stochastic birding" introducing probability considerations into identification? This would be truly something one can work with. Now, many observations are just out of the play.

Click to expand...

I really think you should add some kind of duck or cormorant. It just didn't look that much like a PIWO.

emupilot said:

As for the wingbeat, your data contradicted your hypothesis! You claim that a bird maintaining 8.6 beats per second could be a Pileated, but in none of your test cases does this actually occur. I suspect you are not aware of any case where a Pileated has actually been recorded maintaining the Luneau flap rate, otherwise it would have been in your paper. You can not claim the Luneau bird to be "pretty damn close" to a Pileated wingbeat without a statistical analysis, which I doubt would be friendly to your hypothesis.

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I'm glad now that everyone seems to agree that nothing can be conclusively drawn from the Luneau video, because that was really the point of the paper. the Luneau video had been published as conclusive proof of IBWO. It was important to get something published in such a way that even those who believed the sightings could agree that the Luneau bird was not 100% proof. To play the numbers game, which seems to have become popular here, whether you believe the Luneau bird is 90% likely to be an IBWO, or 50%, or 10% or 0% really isn't the issue, as long as it has become evident that 100% is not a tenable option. What has happened since the Sibley papers and to some extent since mine is that the goalposts moved. From 100% IBWO in 2005 we are at the stage where pro-IBWO people say that if there is a 1% chance that IBWOs persist, we have to assume they do and act accordingly. I wouldn't disagree with that, but the point is that 99% of the argument has been won by the sceptics.

For wingbeat analysis... wingbeats 4-11 only became an issue in 2007. In 2005 we were at a stage where the Science paper was stating that PIWOs had never been recorded flapping faster than 7.5 per second, so the Luneau bird could not be a PIWO. It wasn't as if I trawled the web for months to try and find PIWOs that could flap at 8.5 per second. In fact David Nolin's videos were the first and only ones I ever analysed, and they showed very quickly that one central pillar of the pro-IBWO evidence was false. PIWOs could flap that fast when they are taking off in a panic. That was job done as far as my paper was concerned. It went to show just how ropey and uncontrolled the Science paper was, and suggested that the folks at Cornell hadn't tried very hard to analyse any PIWO videos. Then the goalposts moved again, because suddenly it became important to show that PIWOs could maintain that flap rate for at least the 8-9 clear wingbeats of the Luneau video. OK, so someone can go back and someone can try and find a PIWO flapping at 8.5 per second for 8 -9 wingbeats, but notice that we are now arguing over the last 20% of the evidence, the big 80% (showing that PIWOs can and do flap that fast) is over. I wasn't aware of any such videos when my paper was published. I'm feeling pretty confident now that these and other issues relating to the only objective evidence of IBWOs (audio and video) have been resolved and there is no reason to suspect that any of the evidence relates to living IBWOs. It will all come out in the end. SO it comes down to whether or not one believes the sightings. This is always a matter of opinion, but as far as I can see the top birders, and those involved in rarities and record assessment, are tending to smell a big fat rat on those.

btw see this post from the Secret Freezer. That IBWO at 8.6 per second from the archives is not performing an escape flight similar to the Luneau bird. I actually think it very likely it is stood still and fluttering its wings. How shaky is that to base a belief in wingflaps on?

not so fast

Martin,

In relation to the Luneau video no one but Bill Pulliam has examined the issue of flight mechanics. It is clear to me that the Luneau bird has a different stroke pattern than a PIWO. There needs to be a careful and objective comparison of how Lbird and PIWOs move their wings in a flap cycle. Until this is done I don't believe the Luneau bird can be ruled a PIWO.

The point is that it can't be ruled as "not a PIWO!"

curunir said:

I really think you should add some kind of duck or cormorant. It just didn't look that much like a PIWO.

Click to expand...

Didn´t the bird appear from behind a trunk where it was perched before taking flight? This would be very unlikely for a duck or cormorant.

Unless it was a hole nesting duck..... like a Wood Duck or a Merganser

No. Such an analysis has the potential of ruling out PIWO, so you certainly cannot rule it in now.

Jane Turner said:

The point is that it can't be ruled as "not a PIWO!"

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Louis Bevier's website is now online here.
This confirms among other things that the Luneau video bird's plumage is consistent with pileated, and documents Pileated Woodpecker flapping at 8.34 flaps per second for a full 8 wingbeats.

Cheers Martin

as many suspected, now someone has actually studied the wingbeats of PIWO, there are no surprises.

Empirical evidence demonstrates that the bird in the luneau video flaps at the same rate as a fleeing PIWO

sadly, it will not make a jot of difference to some people.

Tim

I am in awe at your persistance in convincing BF members that the IBWO is extinct Tim. Not sure why or what difference it makes mind you but you have proven yourself to be very persistant... no wonder you can find those rare asian birds, you never quit! Sadly though (for you) I'm not sure you have made any difference in anyones opinions on anything except maybe their opinion of you personally...

cheers mate

Russ

If you can't attack the evidence, attack the people.

First rule of internet debate?

I thought this thread was extinct. Perhaps just critically threatened?

lewis20126 said:

I thought this thread was extinct. Perhaps just critically threatened?

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There's really no evidence that it is extinct. No proper search has been performed - the internet is huge and it may be cached on part of the web where few birders ever go. Maybe even the Cache River. Many threads can go quiet for long periods of time. Until someone can show me another thread that flies like this one, i'll continue to believe that this one is extant.

Thanks, that made me chuckle this morning!

I blame Allwood and The Doc. They've broken all the believers. Spoilsports!.

comatose

Big Phil said:

I blame Allwood and The Doc. They've broken all the believers. Spoilsports!.

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"Broken all the believers"? Don't kid yourself. Driven away? Nah, probably not that either.

My guess is that everyone's fallen into repetition-induced comas.

Sport does seem spoiled though, dunnit? :-C

Don't worry. There will no doubt either be more sightings or more "sightings". Hey, who knows? Maybe even both!

Either way, you'll get your sport back.

Cheers, all. B

- Dave