Hello! I saw these birds (in a group of 4) by a tidal river on the South Coast of England this week (Dec). They were sitting on the bank and when disturbed flew high and were agile in strong wind. They were larger than the gulls also in the area. They returned to the bank, I didn’t see them in the water at all. I’m new to birding and I can’t identify them, they are a bird I had not seen here before. Any ideas? Thanks!