Hi Jon,
These maggots are almost certainly those of a parasitic fly
(Diptera), of the Muscidae family, the most prevalent genus in
Australia being Passeromyia. Bell miners and many other species are
occasionally infested with P. indecora in my study sites in Melbourne
for example. The other main genus of parasitic flies is Philornis,
though this is generally only found in the New World regions.
Excellent work on the fitness costs of these flies is being done by
Kleindorfer and colleagues at Flinders University at sites throughout
the Galapagos islands.
There are three species of Passeromyia in Australia, though none have
been worked on in any great detail beyond taxonomy (see work by
Pont). P. indecora is the most widespread. Reports indicate it breaks
through the nestlings skin and feeds on blood, but apparently only
eats tissue after nestling death, though I'm not 100% convinced of
this. The maggots pupate in the nest before leaving as flies 15 days
later. Only the maggots are parasitic, adult flies eat fruit,
excrement etc, the usual fly fare!
It is a pretty disturbing sight seeing nestlings infested with these
guys, and not a great way to go I imagine! Infestation is not always
fatal however. Interestingly an honours student of mine, Maria Pardo,
did some work on these flies and vigilance in Bell Miners, and found
that birds removed both flies and maggots from their nests, so some
birds at least are awake to the threat and respond accordingly.
Hope this helps,
Paul
On 24/09/2007, at 10:43 AM, Jon Wren wrote:
Gooday all,
Last week a mate of mine contacted me about two dead Yb Sunbirds
that he located in a nest adjacent to his house. The reason he was
drawn to the nest was the adult birds behaviour.
He had been observing the female and the male to a lesser extent
coming in regularly to feed the young but the adults seemed
agitated and reluctent to enter the nest.
On inspection he found the chicks to be dead and two large
creamish maggots on the birds body they had made an opening from
the birds body. He described it as if the grubs had been inside the
chicks and had eaten the way through to the outer body.
Not being an entomologist I could only hazard a guess and thought
it may be the result of the birds being attacked by a parasitic wasp.
Any help anyone may have on this subject would be gratefully received.
Jon Wren
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Dr. Paul G. McDonald
Centre for the Integrative Study of Animal Behaviour
Macquarie University
Sydney, NSW 2109
Australia
Ph: +612 9850 9232 Fax: +612 9850 9231
http://galliform.bhs.mq.edu.au/~paul/
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