Common Scoter
I then paid a second visit to Bruno, the name affectionately given to the Dusky Warbler in Bredene, on day 23 of its extended stay. It was calling as soon as I arrived and I eventually got to see it three times, although always very briefly, as it never stopped in the same place for more than a few seconds. This picture by another observer is fairly typical of the views I was getting but it was still nice to see it again, being the only Dusky Warbler I have ever seen. Already very pleased with this, I had a brief look around Ostend harbour before catching the train home and this gull stood out to me as having a very white head. After lots of deliberation and help from various people, I'm fairly happy this is a second-winter Yellow-legged Gull, another year tick and my 202nd species in Belgium this year.
UPDATE 9 December - Belgium's top identification expert has commented on my gull and it seems it is just a Herring Gull after all! Apparently, the pattern on the tertials is wrong for a Yellow-legged, plus the mantle should be a darker, bluish-grey. This is why I don't usually bother trying to id immature gulls!