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.
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.