Craig Doolan wrote:
>
> If the current number of Blue-billed Ducks at Werribee is more than
> the current estimate for eastern Australia that tends to suggest our
> estimates are a fair way off. Are there still many Blue-billed Ducks at
> other haunts of theirs in eastern Australia and are there simply just many
> more of them than we thought?
I reckon, like the Freckled Ducks, they have had good
breeding opportunities over the last 2 summers (particularly
2001/02) and may have been concentrated by the drought.
Their numbers may fluctuate dramatically and what matters is
the long-run average population (?).
> Good point about the impact of sewage though, especially as some species
> become more and more dependant on sewage ponds as natural wetlands
> disappear, will this become an issue in the future?
Good question. I have not seen any public statement by the
various birding groups associated with Werribee/Western
Treatment Plant but I guess some of the pressures around for
increased human population/development or new forms of
agriculture, coupled with the proper commitments to reduce
the amount of nitrates reaching Port Phillip Bay (by
different types of treatment and water reuse), could combine
to threaten some of the habitats.
Michael Norris
>
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