Agree with Martin that both appear to be Black-necked based on rounded head shape, lack of clear-cut demarcation between black on crown etc and white sides of head, and dark smudgy patches extending down onto sides of head from crown below level of eye. The unusual feature is the very heavy bill on one of the birds, which certainly doesnt fit typical Black-necked but also isnt the right shape for Slavonian either [should be more dagger-like without such a thick base]. Looks like an aberant bill possibly with a growth as suggested by Martin.
Still a very good record. Black-necked Grebe is a very rare bird in HK and two together is a treat.
Mike Chalmers
