Comments: these gulls are thought to be the most southerly breeding Herring Gulls (argenteus) on the Atlantic coast. The next taxon further south is the Cantabrican Atlantic Yellow-legged Gull. The size, structure, bill markings, wing-tip pattern, moult (typically P5 growing, P6 missing) and calls of these Herring Gulls are similar to those of the Cantabrican form. The main difference are:
1) leg colour which seems to be invariably pink in the Herring Gulls.
2) mantle shade which is a paler grey in the Herring Gulls, as they have a shade similar to that of normal argenteus.
Juveniles are generally like typical argenteus but they usually show gleaming white rumps and completely black bills, features normally associated with Mediterranean or Dark Atlantic Yellow-legged Gull.