ajohn

On a trip to Tung Ping Chau on 27th December (2009), a good mix of winter visitors, including:
Grey-backed Thrush - 14
Japanese Thrush - 1
Pale Thrush - 1
Siberian Thrush - possible male seen too briefly for definite ID
Common Blackbird - 2
Unidentified Thrushes - 33
Red-flanked Bluetail - 5
Black-naped Monarch - 1
Pallas's Leaf Warbler - 14
Brownish-flanked Bush Warbler - 10
Russet Bush Warbler - 2

Highlight for me was watching the roosting flock of Black Kites building up in the evening; I counted 155 at one point. A common species I know, but seeing them circling over the island was a real spectacle.

ajohn

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.