Interesting Aythya Duck

Scanning through the Tufted Ducks this morning I came across a Aythya duck that stopped me in my tracks , my fist thought was immature drake Greater Scaup but something wasn't right it seems to small , then immature drake Lesser Scaup went through my mind , having seen and found a couple over the years but then again they were slightly easier they were all adult drakes , but the head shape and bill don't look right. It certainly is interesting and could just be one of those Aythya Hybrids that never get solved possibly a Tufted / Pochard cross maybe. A few phone calls were made and it wasn't long before Andy , Mark and Jack turned up there after we had a lengthy discussion. Also noted today were Little Grebe , Kingfisher ,and passing overhead two Raven , 12 Skylark (scarce at the mere), single Meadow Pipit , Pied and Grey Wagtail .Images below are the best I could manage from the distance it was, it never came close at all. If it stays and moults out it might show its true identity, if anyone has any thoughts at all please get in touch .