Eastern Straits of Gibraltar (Spain) (michahellis)

The main comparison is with birds from Tanger and the Gibraltar area.

Mantle: most are a similar blue-grey to those in the Tanger/Gibraltar area but a minority are a more leaden grey.

Size: significantly larger.

Structure: heavier; more adults (30% as against 7-10% in Tanger) have boxy heads; the legs are generally longer being 80-90% of the height of the body above compared to 70% in Tanger and 100% in Mediterranean michahellis. At rest the heavier heads were not tucked into the neck but were held with the bill pointing downwards as in Mediterranean michahellis.

Primaries: slightly more white with 60% showing a white tip on P10 and 40% a mirror on P9. There is more black on P5 with 75% showing a broad band.

Bare parts: bills were a rather dull yellow with a diffuse orange-red gonydeal spot; legs were a dullish ochre-yellow.

Calls: considerable variation perhaps reflecting the genetic mixing. Most long calls (55%) are of the shrill graellsii type as in Tanger but 30% are guttural, as in Mediterranean michahellis, and 15% are a deep argenteus. Mew calls show a similar mixture.

Moult in adults: in 2001 almost identical to that in Tanger three days later on both primary moult and head markings.

First-years: on a small sample of four, 75% of the tertials were like those in the Canaries with a narrow pale fringe; 25% were different to any found in the Atlantic showing, in addition to the narrow fringe, two slight notches on each feather edge.

Moult in first-summers: as in Tanger, equal numbers had completed primary moult or were in the final stages of the moult with P9 growing and P10 missing. Two out of five showed a pale base to the bill by mid-August.

Second-years: these were quite advanced with mainly yellow bills except for fairly frequent black spots across the gonys; the legs were yellow but the feet retained a pinky tinge. The wings showed a quite dark blue-grey colour in most cases with a pronounced secondary bar and faint markings on the subterminal tail band with remnants of dark markings on the outer coverts at rest. One showed long legs, equal to height of body above, but in general the legs were short, c70% of the height of the body above legs. None showed a mirror on P10.

Moult in second-summers: the timing of the moult was similar to that in adults with P6/P7 the most frequent state and others ranging from P5/P6 to P8/P9. The heads were duskier than those in adults with extensive speckles on the sides of the head and a prominent dark eye spot.

Third-years: these showed a prominent white mark on P10, sometimes a mirror on P9 and a broad band on P5.

Moult in third-summers: the most frequent state of moult was P7 growing and P8 missing. Some still showed mottling on the secondary bar and more extensive spots on the sides of the heads than in adults.