I have had some discussion with Dr David Wells [Wells, D.R. 2007. The birds of the Thai-Malay Peninsula: Vol. 2 (Passarines). Christopher Helm, London] on the behaviour of the Green-backed Flycatchers (Ficedula elisae) with respect to their calls see HERE
I had noted that “when I was checking my audio recordings in the field (playing back the songs to see if recorded well as there were soft) the Green-backed Flycatcher responded very strongly. Obviously these songs are territorial, even when on migration.”
David says “Reliability of finding individuals at regular sites certainly implies the maintenance of winter feeding territories, and other similar species (Yellow-rumped, Brown, Brown-streaked, etc.) certainly do that too. These territories may well be advertised/defended vocally to some extent, also in other ways. I have seen Yellow-rumped take up an exposed perch just at twilight and fluff out the yellow patch which then really stands out in the low light, presumably as a signal.”
This post shows one of the male’s responses to the calls I recorded and was listening to – it would flash the under-tail coverts.
Dato’ Dr Amar-Singh HSS
Ipoh, Perak, Malaysia
18th February 2019