An example of a Lesser Black-backed Gull with black on all 10 primaries. Quite unusual to see because black in adults normally only reaches down to P4/P3 and in some to P2. For me at least it’s only my second example in my collection so far.
It seems to be the standard pattern for YBJB because it was also present in 2013 when it was ringed as an adult.
Green YBJB is a female and was incubating 2 eggs on the day these photos were taken: 8 May 2017, IJmuiden Forteiland, the Netherlands.