Thanks Tung. It's a long way from Western Australia.
I didn't notice the ring in the field, only when I looked at the photos. I find this quite often, the photo captures many things which I don't see in the field. Probably a reflection on my observation skills.
On a related but slightly different theme, I've been wondering why we see Short-tailed but not Sooty Shearwaters in Hong Kong in spring, since they both come from South East Australia.
I wonder if it's because the Short-tailed nests further west, and the birds we see pass up the western side of Australia on migration to Japanese waters. That could bring them through the South China Sea on their way north. If the Sooty only passes up the eastern side of Australia, it would mostly miss Hong Kong well to the east.