[TN-Bird] Re: species apparently in decline (BBS data)
- From: OLCOOT1@xxxxxxx
- To: dfv@xxxxxxxxxx, tn-bird@xxxxxxxxxxxxx
- Date: Sun, 30 Mar 2003 20:00:16 EST
In a message dated 3/30/03 2:44:39 PM Central Standard Time, dfv@xxxxxxxxxx
writes:
> >Jeff,
> >The BBS may not be the last word determining the state of bird population
> >in North America and, it certainly does not comprehensively sample the
> >entire North American Continent. But, I believe that it does sample a
> >significant cross section and accurately reflects bird population trends.
Thanks Dave for your reply,
I do not deny the perception of the declines due to many factors. I agree
with most of the declines and understand the reasons for some. I realize that
you believe them also be true but my question still stands.
> >I agree that the change in habitat on a single route can change
> >significantly over the years (when running a route in middle TN this June
> >I noticed that I had described one stop as a scrubby field but, this spot
> >18 years later is now what I would describe as oak hickory woods).
> >However, since thousands of routes are conducted across the continent,
> >the over all results should reflect the changes of habitat North America.
We are not taking about changes on a single route but the changes on all the
routes that I am aware of and I know there are many across the US. You cannot
believe that the extensive and diverse changes across the US balance out, as
land management, usage and extensive exploitation are certainly not anything
that one could have foreseen even 10 years ago, much less 40 or 50. My
question is not how one feels about the numbers but what techniques or
methods are actually used to over come the biases.
> The fact that the study is a roadside study undoubtedly results in some
> bias but I believe it probably fairly accurately reflects the current
> population trends. Results of studies pertaining to TV tower casualties
> collection and weather radar reflect similar population declines.
Again an opinion, which I don't contend. I also look at the tower kill
numbers and spend much time studying the Nexrad figures. Those methods
present other questions which can be pursued another time and I don't wholly
disagree with them either.
It seems some time back a very serious alert was put out to the birding
community concerning a steep decline in tanagers and asking for all kinds of
observations. It was later shown not to be a valid concern but a
misrepresentation or reading of data. Someone that knows more about it can
correct my old memory about that instance. I Don't doubt the declines, just
wanted to know more about BBS data methods on deciphering the numbers and
thought someone might know.
Asking also as a curious layman, my question still stands..........
Respectfully and Good Birding!!!
Jeff R. Wilson
OL' COOT / TLBA
Bartlett Tenn.
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