Yellow-bellied Sunbird nestlings.

To: Jon Wren <>
Subject: Yellow-bellied Sunbird nestlings.
From: Paul McDonald <>
Date: Mon, 24 Sep 2007 11:08:02 +1000
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,

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

Ph: +612 9850 9232 Fax: +612 9850 9231


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