No it is not possible to identify the species of bird from the leg flag number. This is because we use the same letter-number combinations on each species. Making them identifiable to species would mean that we needed more combinations, which would require smaller letters/numbers (so harder to read) or larger flags (more difficult for the birds). When reporting flag sightings it is necessary to report the species as well as the flag combination (or provide a photo).
The metal ring does have a unique number that allows us to recognise the species and individual involved, but this is very difficult to read unless the bird is trapped.
Your bird cannot be a Wandering Tattler, which has never been recorded in Hong Kong so would not have been flagged here. Grey-tailed Tattler does occur, but has not been flagged with the combination H8.
Only a few species have been flagged in Hong Kong with the combination H8, and most can be ruled out immediately. The most likely explanation is that the bird you saw was a Common Redshank. This bird was flagged on 25th September (2 days before your sighting) and was present until at least 9th October. It was a juvenile, which may be why you thought it looked different from other Common Redshanks. A photo would help us to be certain about the species, if you have one.
