[texbirds] Re: Another Perspective
- From: Jay Packer <jay@xxxxxx>
- To: Texbirds <texbirds@xxxxxxxxxxxxx>
- Date: Sun, 3 Jun 2012 09:17:34 -0500
I posted this the other day, but for some reason it was blocked and
prevented from coming through...
Ted and Joseph make good points, largely aligned to my way of thinking. I
will play devils advocate a bit with Ted's post however.
I agree that theoretically, what Ted has proposed is a testable hypothesis.
Were we to see the pattern he suggests (namely a distribution of rarities
around ports), I would think that this would be strong evidence for the SAH
(ship assisted hypothesis). Much the same occurs in south Texas with a
reasonable number and frequency of birds that seem clearly to be caged or
escaped individuals.
However, the absence of such evidence does not begin to discount the SAH.
Why? Because we have serious limitations on our abilities to judge the SAH.
It may be that all of Ted's three conditions are true, but that such
records occur at such a low number that they simply go undetected by
birders.
When I think about what needs to happen for a rare bird to be discovered,
I'm amazed we find any at all. If the Tropical Mockingbird had set up
residence in the back of Sabine Woods instead of at the entrance, I think
it very well could still be undetected... If the critter had set up shop
100 yards away from Sabine Woods, we'd never find it at all. (I'm not even
sure if there's habitat 100 yards away from Sabine Woods, but you get the
point.)
While I don't begin to consider myself an expert in statistics (in fact,
I'm pretty much a bumbling idiot when it comes to the subject), I do recall
that if a pattern occurs at too small a number or at too low a rate, we're
simply not going to be able to detect the pattern and tell it apart from
random noise.
--
Jay Packer
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