Characteristics of Iberian Yellow-legged Gull: Iberian atlantis
Range:Atlantic Iberia except for the northern Spanish Atlantic coast. Hence in south west Andalucia westwards from Barbate, all of Portugal and Galicia (and possibly also Asturias) in north west Spain.
Appearance: intermediate between Southern atlantis (to the south) and cantabricans (northern Atlantic coast of Spain). A number of other workers including Bermejo and Munilla have studied this form.
Differences for adults from southern atlantis are:
Mantles: slightly paler but still darker than michahellis. There can be a purple tinge to the blue-grey in some southern Iberian birds.
Underwing: the trailing edge is less dusky.
Size: slightly smaller in south-west Portugal and even smaller further north in north Portugal where the size is similar to that of graellsii.
Structure: in north Portugal, the tip of the bill is slightly more tapering with a slighter gonydeal angle.
Primaries: the black triangle is slightly indented in 31% (12% in southern atlantis) of birds and 7% (1%) have a large indent giving a pronounced V-shape to the black; also P9 caries a mirror in 40% (22%) of adults.
Bare parts: the legs show a reduced ochre tint and the gonydeal spot is usually a less intense red, sometimes carrying an orange-red tint.
Calls: greater tendency (55%) for the long calls to sound like argenteus in the north of the cline but, in the area as a whole, similar to the overall position further south because of the tendency towards argenteus in the eastern Canaries.
Moult: in Atlantic Iberia (Bermejo, 1999), the head can appear quite fully hooded with dense and extensive dark streaking extending to the neck as well. The moult is later in the northerly part of the range.
Further north-east in cantabricans, the mantles become paler still (paler than michahellis), the bills become more tapering at the tip, the outer primaries do not so often have the solid black triangle with 100% (38%) showing some indentation similar to argenteus and P9 carries a mirror in 85% (40%) of birds. The calls are much closer to argenteus with 100% (16%) having long calls like this form and 100% (7%) having mew calls like this form.
Immatures: for second- and third-years there is considerable individual variation with some as retarded as Cantabrican and others as advanced as the dark form.
© Nick Rossiter 2001-2003
email: nick.rossiter1 at btinternet.com