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 Dark Atlantic Yellow-legged Gulls 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 gonydeal 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 (85%) a mirror on P9; 70% 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 gonydeal 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 August missing P5 or P6 and growing P4 or P5; 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.

© Copyright Nick Rossiter 1999-2001.