Sorry, Louis, but I don't think anyone will be able to give more information on this bird.
Roseate Terns have been ringed in Hong Kong but not for a number of years. Some may survive, but we can't be sure.
It is more likely that this bird was ringed in Australia. A few birds with Australian leg flags have been seen in HK over the years. But without any idea of the engraving on the ring, or any idea about what (if any) leg flags the bird was carrying, we cannot say for sure.
