kmatthew

These are all ringed birds, which means either the HKBW, other institute researchers or even other societies from abroad have captured them and put a metal ring on their legs to keep track of their migration movements. The ring won't hurt the bird. If you can zoom in and see the number on their legs, it might be possible to help researchers track down these ringed birds and build a more clear picture of how these birds migrate and move in different seasons.