A distinctive form of Yellow-legged Gull on the north Spanish coast was first reported in the 1980s by Teyssèdre. A number of other workers including Dubois and Newell have studied this form.

Range: Atlantic coast of northern Spain (Cantabria, Pais Vasco and possibly also Asturias) and Atlantic coast of south west France near the Spanish border with small numbers in the Royan/Arcachon area.

1. a mantle that is usually paler grey than that of Mediterranean Yellow-legged Gull but darker than that of argenteus; the blue hue is less obvious than in most Southern atlantis and there is sometimes a faint purplish tinge instead.
2. a paler trailing edge on the underwing than that of Mediterranean Yellow-legged Gull.
3. quite a small size, close to graellsii.
4. a lightweight structure with rather small heads, thin snake-like necks, slender bills, thin legs and a flat chest.
5. tapering bills with slight gonydal angle often pointed at the tip.
6. very much reduced black on the wing-tip on P6-P10 giving a V-shaped area of black on the outer primaries; pale edges show on the inner webs when the wingtip is fully spread.
7. extensive white in the wing-tip with always a large mark on P10 and usually (81%) a mirror on P9; 72% of adults have a complete white tip to P10.
8. a thin band or a spot on P5, more rarely a thick band.
9. no mark on P4.
10. In August, bright yellow bills with an orange-red gonydal spot normally restricted to the lower mandible.
11. in August, a bright orange-red orbital ring although Teyssèdre (1983) claims it is always red; more study is needed here.
12. long and new calls like those of argenteus.
13. relatively late period of moult with adults in early August missing P5 or P6 and growing P4 or P5 and in late August missing P6 or P7 and growing P5 or P6; heads appear sparsely marked with brown speckles on the crown, nape and forehead and denser speckling around the eyes in August but are apparently streaked by October (Teyssèdre, 1983); Bermejo (1999) indicates that the head can appear quite fully hooded with dense and extensive dark streaking extending to the neck as well and not dispersing sometimes until January or February.
14. incubation typically in the first half of May.

First-years: structural differences from Southern atlantis are as for adults.

Other features generally fall within the considerable variation of Southern atlantis except that:

• Mantles: most (85%) are reddish-brown or have a ruddy tinge.
• Wingtip: the pale primary window is more obvious.
• Bills: a pale base is frequently (75%) found.
• Rump, base of Tail: quite dull and mottled.
• Later primary moult: most still growing P9 and P10 in early August (second calendar year) when other forms have virtually completed this stage.

In August, similar to Southern atlantis except that the primary moult is later (see above) and the legs are always flesh-coloured with no yellow or straw tinge. By February (see Dick Newell's photographs, below), apparently more retarded than Southern atlantis with:

• Flesh legs.
• Less grey on the wings: in two of the three examples shown in flight, the wings are almost entirely brown-grey with the other one showing grey inner primaries and grey mottling on the lesser and median coverts.
• Some brown feathers remaining in the scapulars and back although these are now mainly grey.
• More extensive, more solid and darker subterminal tail band. In one case out of three, though, the tail band is beginning to break up.

In all three the dark secondary bar and outer primaries are very obvious. The bill is pale from the base to about 70% of its length in two cases and quite retarded in another with only the basal area becoming pale.

These observations are preliminary in view of the small sample sizes.

Typically the Cantabrican birds show more pronounced brown markings than the Southern atlantis being quite heavily mottled on the secondary bar and with an obvious carpal bar and dark markings on the primary coverts. The tail may show faint remnants of the subterminal band and the mantle is a less clean grey colour showing small areas of brown. The bill is usually a bright yellow but the legs can still retain a pinky tinge, giving a rather lurid yellow-pink effect.

As in adults, the Cantabrican Atlantic form has a more retarded moult than the Southern atlantis with third-summers typically having P4 or P5 growing and P5 or P6 missing in early August.

© Copyright Nick Rossiter 1999-2003.

email: nick.rossiter1 at btinternet.com