There is a slightly complex taxonomy about the Japanese/Manchurian Bush Warbler complex. The names have changed several times over the last few years, and the identification of the taxa involved is not clearly understood. Two species are currently on the HK list - Japanese (Cettia/Horornis diphone) and Manchurian (Cettia/Horornis borealis).
This bird has fairly uniform brown upperparts (no grey tinge to mantle) and a relatively poorly-marked supercilium. I think it is the taxon canturians, which is treated as a subspecies of Japanese Bush Warbler.
Do you have any photos which show details of the ring number, which might allow us to work out which individual is involved?
