Adrian, for one horrible moment.......!! That Curlew Sandpiper looked to have an almost identical colour scheme to our Dunlin scheme operating at Ynyslas then, thankfully, I realised you had said a flag!! We have ringed 3 Curlew Sandpipers at Ynyslas recently but don't have a colour scheme registered for them - we don't catch enough to warrant it. The one you photographed was almost certainly ringed in Norway by Kjell Mork Soot. Not sure I should post his email here so contact me if you can't find it on the net. It is listed in the register of wader colour-marking schemes maintained by IWSG (the International Wader Study Group).