Well well Giuseppe,
Very nice pictures this bird, nicely demonstrates late winter / early spring moult in LBBG. Well documented!
From ring recoveries we know moult in the inner primaries, in 3CY spring birds, can be found in all subspecies: of course fuscus and heuglini, but also intermedius and even graellsii (at least NW European continental graellsii).
Example birds can be found on ORG:
fuscus:
http://www.israel.gull-research.org/fus ... rch11.html
heuglini:
http://gull-research.org/heuglini/heug3 ... rch06.html
intermedius:
http://www.gull-research.org/lbbg3cya/svs810679x.htm
graellsii:
http://www.gull-research.org/lbbg3cya/5366282.htm
Upperpart grey tone suggests this is not nominate fuscus.
Something different: Do you have ringed LBBG in your region as well?
Mars