It is rare to see a Lesser Black-backed Gull with black on all 10 of its primaries. But as Green YBJB of our IJmuiden Forteiland colony, the Netherlands, proves, it can depend on when you see a particular individual and which wing you’re looking at.
If you would have seen YBJB in 2017 and 2019, you would have seen it with black on all 10 primaries in both wings.
If you would only have seen YBJB in 2018 or 2020 and not in other years, you would have missed it.
If you would only have seen its right wing in 2021, you would have missed it in its left wing.
And if you would only have looked at its right wing in 2020 you would have seen that only P2 did not have black, which is even rarer.
I have been following YBJB since 2017 and since that time its primary pattern has varied greatly. This year, only P1 in the right wing does not have black.
The following scheme shows for each wing in the last 5 years which primaries had black, and the total number of primaries with black for each wing:
The following images show YBJB in the previous years: