Is it possible that the grebes are being poisoned too, but aren't dying in such
visible places?
Peter Shute
> -----Original Message-----
> From:
> On Behalf Of
> Carl Clifford
> Sent: Wednesday, 8 February 2012 1:52 PM
> To: Chris Watson
> Cc:
> Subject: Re: [Birding-Aus] Botulism poisoning in waterfowl
>
> Chris,
>
> Though Grebes are divers, they feed on crustaceans, fish etc
> and tend
> not to go poking around in the mud at the bottom of the
> ponds. Diving
> ducks tend to ferret around in the bottom mud and would be
> more likely
> to get into the anaerobic layers.
>
> Cheers,
>
> Carl Clifford
>
>
> On 08/02/2012, at 1:28 PM, Chris Watson wrote:
>
> G'day all,
>
> A bit of a technical question. I've been monitoring the
> mortality rate
> of a few species at Alice Springs Sewage Ponds after a spike in
> botulism poisoning last year.
>
> I'm not a biologist, but what I've learnt is that "c" type
> Clostridium
> botulinum bacteria reside and breed in anaerobic muds at the
> bottom of
> the ponds. When we get the warmer weather the amount of bacteria
> increases and bottom feeding birds (swans, diving ducks) can stir it
> up and ingest it, resulting in the increased mortality that
> we witness.
>
> At the moment we are seeing a greater number of dead and moribund
> birds around the ponds (mostly Black Swan, Hardhead, and the
> occasional Grey Teal).
>
> My question is this; why are the aforementioned species affected but
> the grebes (Australasian and Hoary-headed) which are accomplished
> divers have not been observed to be affected to this point. In 18
> months, I have not found a single grebe carcass or seen any grebes
> that seem effected by botulinum toxicity. I am at the ponds at least
> twice a week so have a very good idea of the changes in populations
> and movements there. We have a fairly stable population of
> between 80
> and 120 grebes, and I'm surprised that they never seem to be
> affected
> by this toxin which always seems to take out quite a few swans and
> ducks (and the odd stilt and lapwing) each summer. I can only
> imagine
> that there is some difference in their feeding technique or the
> physiology of their digestive tract which keeps them safe from it.
>
> Can anyone enlighten me?
>
> Cheers,
>
> Chris Watson
> Alice Springs
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