Thanks Peter for the suggestion. Yes there has also been a decline in abundance
of the House Sparrow in Canberra, throughout the years 1981 to 2002 for which
consistently compiled data exist from the Garden Bird Survey (GBS) that has
been run by Canberra Ornithologists Group (COG). One thing to be aware of
though is trends such as this can only be discussed sensibly in past tense.
They can change at any time. Pity I can't include the graph from my book in
here. For years 1 (1981-82) to 14 (1994-95) the Common Starling and House
Sparrow (respectively) occupied position 1 and 2 in the abundance lists (out of
130 to 147 species recorded per year). Actually the House Sparrow was in very
slight increase for the first six years (probably not statistically significant
though) and then fairly steep decline. In year 15 the Sulphur-crested Cockatoo
replaced it to become number 2 species. As at year 21 (2001-02) the Common
Starling and House Sparrow (respectively) occupied position 5 and 6 in the
abundance lists. In 2003-04 the House Sparrow was down to ninth (ref: COG ABR
in CBN). The Common Myna has gone above the Starling, suggesting a very strong
link there but the reason for decline in the House Sparrow is not so clear.
Probably many factors acting together. Not something we need to worry about too
much at this stage. The continuous monitoring of a bird community shows a lot
of variability not just between increasers and decreasers but between stable
and not stable species.
Philip
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