Oriental Reed Warblers used to be common on the river near my apartment, about 7 or 8 singing males or so, but they completely disappeared a couple of years ago.
3 have been singing this spring. At separate locations and not often. Is it just 1 bird moving around? Are they just migrants passing through?
I remember that here in HK Oriental Reed Warblers were ringed in winter, and some of these birds were found – as breeders – in the same small area of reed land in Honshu. Very site specific…..doesn’t solve your query, really
Sadly ours seem to have ‘moved house’!