Given the complexity shown above, in particular the overlap between forms, it is certainly not the intention here to establish new species or even new subspecies. It is, however, interesting to reflect on the influence of well-established species on the various forms. The main ingredient in Dark Atlantic Yellow-legged Gull would appear to be graellsii with the dark mantle, the extensive black in the wingtip, the nature of the long and mew calls and the appearance of first-years. There also appears to be an influence of argenteus in most groups with a tendency for bright bluish-grey mantles, blunt wingtips and shriller calls. Those in the Azores, the western Canaries and south Portugal appear to be most true to graellsii, those in the central Canaries less true to graellsii because of the extra white in the wingtip and those in the eastern Canaries even less true with calls close to argenteus as well. Those in west Portugal and north-west Spain show some transition to the Cantabrican Atlantic Yellow-legged Gull with less black and more white in the wingtip and a tendency towards a slighter structure. The latter is thought to contain genes of Mediterranean Yellow-legged Gull and Herring Gull (P. Dubois, pers. comm.). It also seems probable that there is a Mediterranean Yellow-legged Gull ingredient in the gulls of the Canaries whose adults have relatively pale heads in moult. The more robust structure found in all groups, the tendency for slightly less black and more white in the wingtip in all birds (except those from the Azores, western Canaries and south Portugal) and the less obvious striped inner wings and indistinct pale primary panels in first-years could come from the influence of Mediterranean Yellow-legged Gull or argenteus or simply evolution.

Taking all ages together, the historical confusion in taxonomy of these gulls discussed earlier is not surprising. The Dark Atlantic Yellow-legged Gulls do seem to be a mixture of graellsii, Mediterranean michahellis and argenteus. Given the obvious influence of graellsii on all the Atlantic Yellow-legged Gulls, it is perhaps not surprising that Paterson (1997) reports frequent hybridisation (about 40 cases per year in the early 1990s) of Yellow-legged Gulls with graellsii on the Atlantic coasts of Portugal and northern Spain. An example of a putative hybrid is at Hybrid . Even in Cantabria and the Basque Country, where the Yellow-legged Gulls are more like argenteus than graellsii in terms of wing-tip pattern, mantle shade and calls, there is hybridisation between Yellow-legged Gull and graellsii to a limited extent so the Cantabrican form clearly does also share some affinity, such as in structure, with graellsii.