A few days ago I had the unusual opportunity of photographing all three of our locally occurring Black backed gulls together on the beach at Rock-a-Nore.
In the picture are an adult and an immature Great Black-backed gull, with pink legs, and in the case of the adult, a very black back. In the foreground, the pale backed bird is the race of Lesser Black-backed gull that breeds in small numbers locally, Larus fuscus graellsii, while behind is the much darker backed L. f. intermedius, “Intermediate gull”, which breeds in Scandinavia. Both have yellow legs. There is some variation in mantle shade of these gulls and these seem two fairly extreme examples.
The dark mantled birds are not rare, though most of the LBBGs I see locally seem to be the paler one, I must keep better records…
A third race ,L.f. fuscus, Baltic Gull occurs rarely in Britain-it is darker still [the Helm guide to Gulls, a must for the enthusiast, gives the Kodak Grey Scale numbers for all three races !] and structurally different.