Atlantic Yellow-legged Gulls -- Introduction (March 2003)
There is considerable disagreement over the classification of the Yellow-legged Gulls found in the Atlantic. Dwight classified all the forms found in Macronesia (Azores, Canaries and Madeira) and in Atlantic Morocco as atlantis. Stegmann extended the range of atlantis to also include the coast of Portugal. Bannerman also included Portugal and Morocco within the range of atlantis. Since this time a number of partial studies have been made which placed the Portuguese and Morocco birds with michahellis (Mediterranean Yellow-legged Gull). A recent study by Yésou even placed the Canaries and Madeiran birds with michahellis but this relied upon misquotes from the literature and ignored aspects such as biometrics, vocalisations and wingtip patterns.
From personal studies at many sites on the Atlantic seaboard, the position of Dwight is verified to some extent with the gulls of the Canaries, Madeira and the Atlantic coast of Morocco forming a coherent group termed Southern Atlantic Yellow-legged Gull -- Southern atlantis. To the north is found a closely related form Iberian Atlantic Yellow-legged Gull -- Iberian atlantis. The biometrics and vocalisations of these forms are broadly similar and very different from those of michahellis, a term best reserved for birds from the Mediterranean.
All of Atlantic Iberia is occupied by Iberian atlantis except for the northern coast of Spain in Cantabria and Pais Vasco. Here a form occurs called Cantabrican Atlantic Yellow-legged Gull -- 'cantabricans' or bernisi -- which is so similar to Herring Gulls in many respects that it could even be classified as a form of argenteus.
Less is known about the Azores form but much has been speculated upon its characteristics. It has a few characteristics of its own and other characteristics are a mixture of those found in Southern or Iberian atlantis. It is tentatively considered as a form in its own right: Azorean atlantis. More data is needed for an objective placement to be made.
In the Straits of Gibraltar (Andalucia in Spain, Tanger in Morocco) intermediate forms occur between atlantis and michahellis. This is the intersection zone between the two forms.
Other current sources of information, besides these web pages, include:
Robert Lewis' Lewis Birds.. Bob also agreed with an extended atlantis range after seeing Yellow-legged Gulls in Portugal in the field.
Jonsson (1998). He also thought that birds breeding on the Atlantic coast of the Iberian peninsula and Morocco stand morphologically closer to atlantis and are better treated as such.
Yellow-legged Gulls in Madeira (Keith Regan, Ian Fisher) at Madeiran Atlantis
Yellow-legged Gulls in the Azores, Madeira and Morocco (Theo Bakker) at Cursorius
Yellow-legged Gulls in west Portugal (Dick Newell) at Dick's Birds
A total of 22 weeks study over 13 years in the field mainly late March-September with one visit in December.
Iberia: south Portugal (Faro), west Portugal (Setúbal, Porto, Matosinhos, Minho), northern Spain (Santander), south west Spain (Sanlúcar, Cádiz, Conil, Barbate, Tarifa, La Linea), south east Spain (Estepona, Nerja), Gibraltar.
Morocco: Atlantic coast (Tanger, Asilah, Essaouira, Agadir).
Macronesia: Madeira including Porto Santo, Canary Islands (Lanzarote, Graciosa, Fuerteventura, Gran Canaria, Tenerife, Gomera, El Hierro, La Palma).
France: south west (Royan).
Bibliography: about 80 references
© Copyright Nick Rossiter 1999-2003.
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