After having already observed a presumed hybrid Lesser Black-backed Gull x European Herring Gull while checking one of my local gull patches this morning, the next location that I checked presented a first-calendar year Yellow-legged Gull Larus michahellis as well as a first-calendar year Caspian Gull Larus cachinnans.
Yellow-legged Gull
Caspian Gull
I was delighted with this observation because Caspian Gulls at this time of year in my local town are pretty rare; they are normally seen during the winter although it has to be said that only a handful of local birders actively follow gulls so many more may go unnoticed.
Note the new greater coverts and lesser covert.

1st-calendar year Caspian Gull (right) with 1st-calendar year Lesser Black-backed Gull (left). Leiden, The Netherlands, 10 August 2013.