Whilst I agree with previous posts that it is totally up to the finder of any bird, be it rare or not, whether they share the location to other people personally I don’t understand why they would not want to.
The main reason I have heard are disturbance yet in the UK it is not unknown for 1000 people to turn up at a rare bird at the same time with no adverse effect. In HK if 30 people turned up at the same time that would be unusual. If somebody is deliberately disturbing the bird then there are plenty of forums to name and shame that person as has been done in the past.
From my experience the majority of birdwatchers in HK are very keen to share their finds with fellow birdwatchers even to the extent that special arrangements have been made to access private land the past
Personally if I was lucky enough to find a rare bird I would make every effort to ensure as many people saw and photographed it as possible however is it right that somebody who decided not reveal the location of a rare bird they found goes and see birds other people have found and shared with the birding community.
HK Twitcher