In the 80's I analysed some of the annual bird counts made
by the QOS around Brisbane from 1972-1983.
These were conducted in October each year, with teams of
observers covering a large area in one day.
The numbers of obervers varied from year to year and they did
not always following the same routes.
These methods were clearly not ideal (!!) and nos of birds
counted were corrected to nos/observer. This is a rough and
inadequate correction and would only detect major changes
in bird populations, but that seemed to be the
case for Cattle Egrets (CE).
Numbers of CE in coastal areas were more or less constant over the
12 year period but nos in inland areas (still east of the Great
Dividing range) showed an exponential increase,
Coastal nos/obs inland nos/obs
1972-75 7.3 0.39
1976-79 11.3 7.56
1980-83 9.0 20.5
No other species of heron or egret showed such dramatic changes
in nos. While the data are very rough I think that they do show
the expansion going on at that time.
The origin of the birds is another question.
Cheers
Pete
Dr Peter Woodall email =
Division of Vet Pathology & Anatomy
School of Veterinary Science. Phone = +61 7 3365 2300
The University of Queensland Fax = +61 7 3365 1355
Brisbane, Qld, Australia 4072 WWW = http://www.uq.edu.au/~anpwooda
"hamba phezulu" (= "go higher" in isiZulu)
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