Thanks for the various comments on this. I suppose I should clarify two
things. In this case I don't think it fair to blame the media: newspaper or
TV, for reports on this. I am not complaining about the Sydney Morning
Herald showing this. They could hardly be expected to know the problems
behind the study. I am not criticising the idea behind the study either.
Even though "The Project" on TV last night ran a rather trivialising segment
on this and the film shown in the background again appeared to confuse
between the Common Myna and Noisy Miner, flipping from one to the other in a
way that would confuse many people. These are two separate but slightly
paralleled problems.
The errors are not from bad reporting but bad science. My complaint was
about that the GBS data was significantly misrepresented, more in the
methods and interpretation, than in the results. Then the calculations done
and conclusions applied are well beyond the capacity of the data. As it was
me who created (not the GBS but) the GBS database and compiled all the data
for the first 21 years (1316 observer years of data) and wrote up the
analysis of the survey, I am uniquely placed to comment on this. For what it
is worth, I bring to notice these extracts from The GBS Report (page 49 on
the final section of the introductory part, before the species texts). For
those unfamiliar, The GBS Report is 130 pages of detailed analysis of the
survey. These advices (next two paragraphs), that I wrote in about 2000 to
2002, were not mentioned in the relevant paper and so I suspect were not
considered. I believe that the GBS data were not properly taken in context.
Normal process is if the authors disagree with the advice from the most
relevant prior document, that is fine, but they should mention and discuss
why it is that they disagree with it.
It would be wrong to interpret too much cause and effect in these data,
though there are suggestions of linkages. Most obvious is that the increase
in the Common Myna matches a decline in the Common Starling. Both species
are likely to reach a steady state in the top ten common species (unless
some action is taken). Over that time, most of the larger parrots have
increased drastically, even though the Common Myna has been strongly
implicated as a nest competitor.
The GBS method is designed as a monitoring tool rather than experimental
science. By collating the data in structured ways, measurable conclusions
can be drawn from it. Both the method and the data built up from it provide
a useful system for assessing the effectiveness of any management action
that may be targeted towards particular species. Lastly, the results of the
GBS need to be taken in context. ............ That is the main reason why a
detailed account of the overall results of the GBS was provided prior to the
species description section. It also tells a fascinating story.
Philip
-----Original Message-----From: Dave Torr Sent:
Monday, 13 August 2012 3:05 PM
To: Philip Veerman Cc: Birding Aus Subject: Re: [Birding-Aus]
Common Mynah Study
Excellent response Philip - I have long learnt that newspaper articles on
subjects that I know something about (birds and computers) are nearly
always wrong - so I assume the rest are as bad as well. I seem to recall an
article in The Age on birds on Mud Island in Port Phillip bay that invented
a new species of Egret....
Would be good to write to the paper with this detail - although they will
probably ignore it.
On 13 August 2012 14:44, Philip Veerman <> wrote:
This on-line article Published in the journal PLoS One (see
http://www.plosone.org/article/info%3Adoi%2F10.1371%2Fjournal.pone.0040622,)
is most unfortunate. If you read it at all, I recommend great scepticism.
This study uses data from the Garden Bird Survey (GBS) but severely
misrepresents the way the data were collected. For that and several other
reasons, I believe this study is multi-flawed. I am the author of the book
"Canberra Birds: A Report on the first 21 years of the Garden Bird Survey",
(in short The GBS Report) which I regard as a fitting tribute to all those
who have contributed to the Garden Bird Survey (GBS). This book is a
detailed analysis of the history, methods and results of the GBS that has
been run by Canberra Ornithologists Group (COG) in Canberra, since July
1981. On a personal note, I am angry that this myna article was released
without being checked and verified (by someone who knows, such as me) as a
true representation of the data methods of the GBS.
The GBS Report is cited in this on-line article but clearly was not
consulted properly let alone understood. The article then goes on to make
several major errors in understanding the data framework.
The way it states the GBS was run (stating it as fortnightly surveys of 20
minutes) is a nonsense. It is and always has been since 1981, data collected
on a weekly grid, for unlimited time (i.e. up to 10080 minutes per week,
even though many observer weeks would be only from one to 10 minutes of
effort). This is clear from any one of the something close to 2000 GBS
charts that have been printed, let alone the full description of the methods
and history of The GBS Report. It says "a total of 74 492 surveys was
undertaken in the survey area over 29 years". Not so. The GBS in its
totality is ONE survey. 74 492 is simply the number of observer-weeks (up to
year 29), which is a week on a chart with a record for at least one species.
That is not a survey. They describe the survey area as 3.142 ha, as though
all the contributors have uniformly selected the size of the area to 4
figures of significance and all equally keep to that area for all species.
The best that could be said is that observers variably set a survey area
based on the recommended 100 metre radius, but as this is a volunteer survey
and in the first 12 years this 100 metre radius instruction was very vague,
this is far from consistent. There is little if any understanding of the
geographic or time issues involved, or the way that the survey has evolved.
The way they have used the data after subdividing the area geographically
over time is I think ridiculous, given the way that distributions and
numbers of observers has changed substantially over the years. There is
little attempt to explain the wonky ideas proposed and used, such as why
they translate a 100 metre radius to a square kilometre, as though habitat
spread is even, which it is not and even if it is, it is highly questionable
that every species has been equally counted to the same area. There is
little attempt to justify the rationale behind the species chosen to be
analysed. It seems unaware that there is a huge range of factors impacting
separately or together on every species, that influence perceived changes in
status (not just the addition of another species). Perceived meaning real
and then as revealed after imposition of survey biases. I submit that the
analysis is way over the top mathematically, doing calculations that go way
beyond the real usability of the actual data. To call the article "Empirical
Evidence" is way beyond the truth. At best all that can be said is that
there is some correlations in time between the observed changes in the
distribution and abundance of mynas and other avifauna. To an extent some of
the analysis and conclusions are of interest.
The SMH article mentions: the results show that even when taking into
account the capital's urbanisation, the myna's arrival has reduced numbers
of cavity-nesting birds such as the sulphur-crested cockatoo, crimson
rosella and laughing kookaburra. Yes the Kookaburra has declined but the
Sulphur-crested Cockatoo and Crimson Rosella have had consistent and
significant increase in abundance throughout the period. The Eastern Rosella
has been remarkably stable and the Red-rumped Parrot has been variable.
How do these conclusions from the article make sense? "The abundance of the
Common Starling appeared to increase after Common Myna establishment. Common
Starling abundance declined throughout the survey period. We found no
significant negative relationships between Common Myna establishment and
Common Starling abundance." It is abundantly obvious that the Common
Starling decreased as the Common Myna increased, that is described in The
GBS Report as the most likely relevant interaction to any other species by
the Myna. And what about the activities of Canberra Indian Myna Action Group
Inc (CIMAG see indianmynaaction.org.au) and the culling program of Mynas
being run and the huge reduction in Myna numbers that it has achieved in
Canberra in recent years such that the rise in abundance has been halted and
reversed. (So Carl we certainly do have a control measure.) Why is that not
mentioned? Why is there no discussion of reversal of trends on other species
occurring along with the success of this program?
Lastly I will mention you can do any level of calculation you like with any
set of numbers. I expect that this same analysis would find a strong
connection between the numbers of Common Mynas and the number of mobile
phones or that the numbers of Common Mynas had no impact on the number of
vintage cars. The analysis might have a strong basis if all sites had been
equally surveyed by the same methods for all species equally over all years.
Not one of these aspects is correct. By all means read this article but with
caution or with The GBS Report to properly explain the context of the data.
Philip Veerman
24 Castley Circuit
Kambah ACT 2902
02 - 62314041
Dear B-A,
There is a piece in the Sydney Morning Herald's web site regarding a study
on Common Mynah and their effects on native bird species.
http://www.smh.com.au/environment/conservation/pushy-myna-birds-a-major-nest
<http://www.smh.com.au/environment/conservation/pushy-myna-birds-a-major-nes
t-pest-20120812-242v2.html>
-pest-20120812-242v2.html The study was based partly on data collected by
the Canberra Ornithologist's Group. Now that we know they are a pest, it
would be nice to come up with a control measure - that's the rub.
Cheers,
Carl Clifford
===============================
===============================
To unsubscribe from this mailing list,
send the message:
unsubscribe
(in the body of the message, with no Subject line)
to:
http://birding-aus.org
===============================
|
