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Hi Kathy,
Well of course strictly speaking the bird
should be within the 100 metres. Often you don't actually know whether it
was or wasn't. In a case like that, if it is potentially within the area, I
would put it in. There is little doubt that over the history of the GBS in most
cases, where a person has observed (seen or heard) the bird from in their area,
eg, from in their own yard and it was some distance that may have been close to
in or out of the 100 metre limit, then they would put it on their GBS chart. On
the basis that that is surely what has happened in the past I believe we should
continue with it. If we change the input method, that would lead to biases
in the results. We collect data that otherwise we would not have. This
contributes to the whole picture. It is especially useful to do that for birds
occurring at low densities, such as owls.
The issue has never been delved into in print,
apart from in my GBS Report. My GBS Report covers this issue on page 21 and this
discussion even singles out the Boobook as of particular relevance to the
problem (see the index). The GBS Report makes it clear that in using the data,
one needs to be aware that there is some scaling in the results and one needs to
be aware of possible skewing and biases. But just about all bird surveys have
some problems like this. The Book "Birds of Canberra Gardens" of course misses
this point totally. Let us see whether the mythical (promised "now" over
two years ago in August 2003), COG review of the GBS, that should only have
taken a few days to prepare, given that the full analysis job had already been
done, has anything useful to contribute that isn't just a repeat
or plagiarism of what is in the GBS Report. I doubt it.
Philip
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