Wedge-tailed Eagle over Hughes & GBS interpretation

To: "'Mark Clayton'" <>, <>, "'Canberra Birds'" <>
Subject: Wedge-tailed Eagle over Hughes & GBS interpretation
From: "Philip Veerman" <>
Date: Sun, 31 Jan 2010 23:44:51 +1100
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.
-----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!




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