Nice shot, Horace! Ya... The BTB is skittish in HK too. It will take off if there is a minor movment. This is very common in HK and can be seen flying around in HK country park. Just like our SG Common Palmfly
Bobby,
Another species which I think is common in Hong Kong but not in Singapore is Chocolate Royal (Remelana jangala). Did you see this other species there in HK?