Mark
is quite correct to raise the question. Although clearly the whole question Mark
raises is certainly not new. The answer is that all pieces of data need to be
considered, relative to the way the information were obtained. The
issue is well covered in the GBS Report (probably not mentioned at all in
Birds of Canberra Gardens, which ignores advice on understanding the
survey (at least the 2000 edition did, and I have not looked to see if the
latest one does any better). The issue Mark mentions was also hinted at in
the questionnaire survey I did and analysed, in 1988, of all then GBS
Participants (something like 80 people I think).
Obviously Wedge-tailed Eagles are not a garden bird and the clear
statement has been made as such for many such species in the GBS Report. So
if we are not to include them in the data collection, the question then becomes
where do you draw the line. Should the Yellow-faced Honeyeaters migrating
over the house not be included unless they stop to perch and how to count them
when some do and some don't? Surely the swifts and swallows feeding over
the house are using the environment as much as those of other species sitting on
trees in it. We should not discount them because they are not arboreal or
terrestrial. If we want the results to reflect only those that stop and use the
environment to be included then if that was the instructions for the survey,
well then fine, do that instead. It would completely change the character of the
survey to something serving a totally different function. The survey would then
be smaller in scope and probably less interesting or fun. That is what the BOCA
Birds in gardens survey did. And that survey was totally valid in its own right.
The group that devised the rules of the GBS in 1980 -1981 (long before my
involvement) decided on including all species in or over the 100 metre radius. I
chose to make it clear later that this should be a cylinder rather than a dome,
simply because a dome is much too difficult to assess. Beyond that, it
becomes absurd to devise a set of instructions that cater to all possibilities
of using and asks too much of the observer to decide is the bird "using" the
habitat and so many species would be left out. Remember that the GBS also was
promoted so much in its early days as being a good way to train and encourage
relatively inexperienced observers. So if it was too hard it would be a failure.
About
the breeding record listed for the Wedge-tailed Eagle, surely that is an
observation of display. The COG record people decided to include "display" in
the general codes for breeding, years ago. So (after discussion of course)
I devised the GBS chart instructions in version 3 (and later) to make the GBS
instructions on recording breeding to match the general COG records system. Do
have them different within the same club would be silly. This is also explained
at length in the GBS Report.
I can
only stress that to be useful the GBS system should only be considered in
context of the instructions and history and along with an understanding of the
variability of observer effort, skill and locations put into it over the
years, which is why I devoted so much time and effort to explain these
things.
Philip
-----Original Message-----
From: Mark Clayton
[
Sent: Sunday, 31 January 2010 8:33
PM
To: 'Philip Veerman'; ; 'Canberra
Birds'
Subject: RE: [canberrabirds] Wedge-tailed Eagle over
Hughes
Good evening
all,
For a long time I have
been intrigued by what species are actually being classed as “garden” birds in
the ACT. To me a garden bird is something that actually USES my garden, not
something that has flown half a kilometre up and over the top. How many people
have actually had Wedge-tailed Eagles land in their garden or within the
prescribed area used for GBS recording? In the latest edition of “Birds of
Canberra Gardens” there is even a breeding record listed that I find rather
unbelievable. There are numerous species recorded in the book that I cannot
accept as garden birds – several other species of raptors, both swift species
unless they have actually landed in a tree (which at least some do at night to
roost), grebes, pelicans, spoonbills, snipe etc, etc.
I am not trying to
start an argument with this; I’m just trying to work out what is a “genuine”
garden bird and what is not.
Rational discussion
welcomed!
Mark
