There are numerous different kinds of gulls, but with the known regions of Middle-earth lying on the northeastern shores of the Great Sea, presumably the gulls found there would have been the same that are common in Europe today. Notable among these would be the common gull (Larus canus), the herring gull (Larus argentatus) and the black-headed gull (Chroicocephalus ridibundus), though many other kinds are also found in this wide area.

The word gull is a rare case where an original Anglo-Saxon word was displaced by one of Celtic origin; in Old English the name for birds of this kind was mæw. Indeed, gulls are still very occasionally referred to as 'mews', and Tolkien uses that old word in The Lord of the Rings (in the Lay of Nimrodel, there's a reference to 'mew upon the wing', in The Fellowship of the Ring II 6, Lothlórien). Over time the Anglo-Saxon word mæw was overtaken by a Celtic word related to Welsh gwylan, giving rise to modern English 'gull'.