Mixed species feeding flock

Ever noticed how the bush can be almost devoid of bird song one moment and then you are suddenly surrounded by a cacophany of different sounds? Mixed species feeding flocks are a common phenomenon in our woodlands and forests. This morning, in the Muckleford State Forest I came across such a flock. It comprised Buff-rumped Thornbills Acanthiza reguloides, Little (Yellow) and Striated Thornbills, a Grey Fantail and some Spotted Pardalotes, all moving together in search of insects.

Buff-rumped Thornbill, Muckleford State Forest, 2nd April 2010

There has been lots of research into this behaviour, exhibited by insectivorous birds around the world. In Australia it seems that Thornbills often function as “nuclear” species around which a diversity of “satellite” species assemble. Why do they do it? Feeding in a mixed flock seems to confer advantages to participants including access to more food as the moving flock disturbs insect prey. The different species in a mixed feeding flock occupy seperate habitat niches, with some feeding outside the canopy (e.g. Fantails), others gleaning insects from leaf surfaces (e.g. Pardalotes) while the Thornbills feed in and around the canopy. It’s a great way to quickly see a variety of species up close.

Read an article by Chris Tzaros on mixed species feeding flocks in Land for Wildlife News from July/August 2002.

5 responses to “Mixed species feeding flock

  1. Chris Timewell

    We had our first mixed flock moving through our suburban 1/4 acre property in central Castlemaine on Easter Monday. It comprised Superb Fairy-wrens (~6), White-browed Scrubwrens (2), Silvereyes (~5), Yellow Thornbills (2-3) and a Yellow-faced Honeyeater. The fairy-wrens, scrubwrens and YF Honeyeater were all first records for our house. House Sparrows were also feeding nearby, but I suspect they were our standard residents rather than part of the mixed flock.
    The niche hypothesis makes sense, as they all seemed to be feeding in different areas or on different resources. Does the research on mixed flocks suggest anything about a ‘predator vigilence’ advantage from being part of a larger flock?

  2. Hi Chris – thanks again for the note. I have seen quite a few different flocks over the past few days but your local observation is different again. I have added a link to a LFW note (by Chris Tzaros)to the post and will try and dig up a couple of journal articles over the next few days re predator vigilance. Happy to pass these on if you are interested.

    Cheers, geoff

  3. Thanks for the link Geoff. A nice little article on mixed flocks. The bottom of the first column does mention something about improved predator surveillance within the mixed flock. (This LFW issue also has some good articles on propogating Themeda, and building bat nest boxes!)

    Please don’t go to any trouble to hunt up the journal articles, but if you do happen to find them I would be very interested.

    Chris

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