Hello, Birders.
Norm Erthal writes:
> I have seen rufous-collared sparrows regularly singing in Costa
> Rica in January and Peru in October which is outside of the
> seasons mentioned by Ted.
(October is spring in Peru. But it's pretty close to the equator. Like Costa
Rica.)
> So many that I have a hard time making much out of
> the spring/summer idea. I disagree with the null hypothesis
> of being wild.
I note here that the choice of the "correct" null hypothesis in any situation,
although often a surprisingly complex matter, is not usually one of opinion ("I
disagree..."). There are dozens of books and probably thousands of papers on
starting off with the "correct" null hypothesis.
> I feel the null hypothesis should be escapee or release unless
> there is solid evidence to the contrary.
!!
If you have "solid evidence," then there's no need for any hypothesis--null,
alternative, or otherwise. You start with a null hypothesis (a bird is wild, a
defendant is innocent), and then you present evidence to the contrary (the bird
has a band, the defendant's DNA was at the crime scene).
As of now, I would say we have no evidence--one way or the other. We have
opinions, for sure. All we know is that there's a Rufous-collared Sparrow up
there in Georgetown, Clear Creek County.
> This was the approach taken with the thick-billed parrot in New Mexico
> recently.
I think it was the other way around. To the extent that I'm aware of how the
ABA Checklist Committee evaluated this record, I'd say they did a good job of
refuting the null hypothesis of wild origin. They started out by asking, in
effect, "Why isn't this a wild bird?" And then they presented various lines of
evidence that the bird was indeed *not* wild. I should note here that not
everybody was satisfied with that decision! And that's a key point about
science, about life in general, and, yes, about bird records committees.
Hypotheses, even after they have received extensive testing, remain fluid and
dynamic. You never know... Oh, sure, there's this gradual progression from
hypothesis to "theory" to "law," but even our scientific "laws" (gravity,
evolution, the germ theory, the atomic theory) our forever open to
reinvestigation and reinterpretation.
> The Tufted Duck several years ago would likely have been assumed to be a
> wild bird until it was enticed off the water with feed and a ty-wrap was seen
> on the leg.
Excactly.
That's precisely my point.
The null hypothesis was that the bird was wild. I believe that was the correct
null hypothesis. Then, somebody saw a tie-wrap on the leg, and the null
hypothesis was considered to have been rejected in favor of an alternative
hypothesis for captive origin.
I believe the same approach should be taken for the Rufous-collared Sparrow in
Georgetown.
Note, by the way, that I am *not* saying the null hypothesis should always be
that a bird seen in the wild is, in fact, "wild." In an earlier posting, I
presented the scenario--and it's entirely realistic--of encountering small
numbers of Common Grackles and Indian Peafowl around your picnic table at the
Denver Zoo, Denver County. In that event, I would go with a null hypothesis of
wild origin for the grackles, but I would go with a null hypothesis of captive
origin for the peafowl. See http://tinyurl.com/62b64fq for justification of
those two, opposing null hypotheses.
In the case of the Rufous-collared Sparrow, I think there's at least a little
room for doubt--unlike the case with Indian Peafowl at a picnic table at the
Denver Zoo.
Alls I'm looking for is some evidence! In that regard, I hasten to point out
that Paul Handford has provided us with the most important line of evidence to
date against the theory of "natural vagrancy" or "wild origin." Based on what
we can see in online photos, the bird appears not to be one of the highly
migratory austral subspecies, e.g., chilensis and australis. Perhaps that alone
is sufficient to rule out "wild origin" for the bird in Georgetown.
But what's not sufficient is to say, in effect, "I or we hereby summarily
decree, by fiat, that this bird is of captive origin, and that no further
discussion of the matter ought to be entertained." Wrong. Instead, what needs
to be done now is to amass evidence to refute the null hypothesis of captive
origin. Figuring out the bird's subspecies is an excellent first start. Finding
a tie-wrap on its leg would be pretty good, too. Discovering and interviewing
the guy who ditched it from his RV while getting gas and donuts in Georgetown
would be another nail in the coffin. Et cetera.
Ted Floyd
[email protected]
Lafayette, Boulder County, Colorado
--
You received this message because you are subscribed to the Google Groups
"Colorado Birds" group.
To post to this group, send email to [email protected].
To unsubscribe from this group, send email to
[email protected].
For more options, visit this group at
http://groups.google.com/group/cobirds?hl=en.
