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Ah yes but I don't know of any bird survey that has
in effect one set of rules for one particular species and a different set of
rules for all other species. The issue of recording numbers of Yellow-faced
Honeyeaters has been discussed in detail in the GBS Reports, so biases and
constraints in understanding and interpreting the data are well documented. (I
don't think it is mentioned as an issue in BOCG.) It is acknowledged to
be awkward and that there is the temptation - to be avoided - of adding the
number present at one time to the number present at another time - say five
minutes or three days later.
The GBS method is to use the count as though you
could know when the number of birds in your area hits the weekly maximum and
then take one photo i.e. an instantaneous record, of all the birds present in
the approx 3 hectares and count them all. With the complication of doing this
process separately for every species. Obviously you can't do that, entirely
correctly as it is too difficult. With difficult species, the best we can get is
a good estimate. However this is an attempt to establish a population density
figure, the number of birds that the area can support at one time. This is very
different from a tally of birds passing through the area over a period of time -
and then there is the issue of what period of time? If the survey is to have any
kind of value into the future, it is best to retain the same methods. I have the
documentation to show that when the rules were devised, and if not then
certainly when they were clarified, for the launch of Version 3 of the chart in
1993, this issue was given serious thought, so the reviews have been done.
Not only has the current GBS method and the GBS report received very strong
endorsement in many published reviews and citations around Australia and the
rest of the world but several other clubs are thinking of adopting the current
methods of COG's GBS for their own surveys. So this is a trendsetter.
If we wish to compile a tally of Yellow-faced
Honeyeaters moving along their migratory route, then COG has developed a very
good protocol for that purpose and we have used it in our honeyeater surveys
over many years. We should use that. It is more fun to count those birds at this
time using that method than the GBS method but it is for a different purpose
(little to do with population density), unlike the GBS (which is concerned with
population density). Or to quote the _expression_: "horses for
courses".
Philip
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