Both species are fairly common, mostly in the eastern New Territories and some of the offshore islands (where the habitat is more suitable).
I suspect that there was an element of the species being overlooked in the past, when observers were not familiar with the calls (as I expect you've noticed, the birds are usually very difficult to see and are mostly recorded by call). There may also have been a real increase in HK, as boh species started breeding here relatively recently and it seems unlikely the distinctive and obvious songs have been overlooked.
