South Morocco (michahellis)

Mantle: slightly paler; still a dark blue-grey but the contrast between the tip and the wing is greater than in birds of the central Canaries. However, the mantle is still probably darker than that of Kittiwake Rissa tridactyla.

Size: smaller, similar to graellsii.

Structure: in general slighter, only slightly heavier and slightly more muscular in appearance than graellsii with a modestly protruding chest (particularly wide at the base), a slightly less attenuated appearance, a slightly heavier cylindrical bill with a stubby end and distinctly thicker legs The wings are narrower up to the carpal and appear long as in graellsii but the wingtip remains blunt. A small minority (about 10%), as in the central Canaries, have distinctly heavy features including powerful squarish heads. Their legs, however, are still relatively short compared to Mediterranean Yellow-legged Gull.

Primaries: in April the white tips on the folded wing are generally smaller than those in Mediterranean michahellis, being similar to those in graellsii.

Calls: as in the central Canaries in both pitch and the angle of delivery. Etchécopar & Hüe (1967) describe the gulls of Morocco as having ‘piercing voices’, perhaps because of their shrill long calls.

Direct Comparison with first-summer Lesser Black-backed Gull: south Moroccan birds are generally slightly larger and slightly less attenuated; they have thicker bills with a stubbier tip, heavier heads and chest (the latter more protruding) and whiter heads with the main concentration of marking in April on the eye with speckles elsewhere particularly on the back of the neck.

Moult in first-summers: all primaries apparently still intact on first-years in first visit in mid-April (11th-18th). In larger samples in the second visit in late April (23rd-30th), 50% showed no moult in primaries but the others were in active moult fairly evenly distributed from P1 missing to P3 growing/P4 missing.

Second-years: in April, as in the eastern Canaries.

Third-years: in April, as in the eastern Canaries except that none were found with dusky heads and pale bare parts.

Information needed: moult in adults.

Comment: Urban, Fry & Keith (1986) mention that a dark form of the Herring Gull L. a. michahellis also occurs in north-west Africa (Cape Verde Islands, Senegambia), depict a bird with a deep blue-grey mantle and speculate that this is atlantis. This form is described as smaller than michahellis and is depicted with a rounded head, long, narrow wings, a solid black triangular area on the outer primaries and obvious mirrors on both P9 and P10. These features are typical of those found in south Morocco in the present study except for the markings on P9/P10 which were found in only 25% of the adults seen. Bermejo (pers. comm.) reports that the birds breeding further south in Western Sahara are similar in size and mantle shade to those of south Morocco.