General description:

Sub-adult michahellis (in 4cy and 5cy) may resemble birds in adult plumage. On average, 4cy birds normally still show a few immature features, but on the other hand some 4cy match the average adult very well and are hard to identify. Nevertheless, some of the following characteristics can often be found in 4cy birds:

• The bill is not saturated orangey-yellow, but pale yellow, especially towards the very tip and the base of the bill.
• The bill often has obvious black marks on the upper and lower mandible near the gonydeal angle.
• The red spot on the gonydeal angle doesn't reach the cutting edge of the lower mandible. In older birds this red spot extends on the upper mandible.
• The iris is peppered or speckled, unlike the plain yellow iris in most older birds (5⁺cy birds).
• Some old wing-coverts have a brown hue, especially visible in the outer lesser coverts or central greater coverts.
• The central and lower tertials and outer secondaries show patterns commonly found in third generation feathers: the tertials have dark centres with vermiculate spaghetti pattern towards the fringes and the outer secondaries show a brown hue on the centres, unlike the plain grey fourth generation secondaries found in 5cy and older michahellis.
• The primary coverts show an all-dark brownish centre with a small paler crescent on the tip. In older birds these primary coverts are all grey or at least show a grey base with sometimes some black (an accentuated shaft). Black in the primary coverts in 5+cy birds is often related to the size of the black on the primaries, which may "extend" on the primary coverts.
• The white tip on P10 doesn't merge with the mirror but is separated by a broad sub-terminal band and even P5 shows a broad black patch. In older birds the black sub-terminal band on P10 is much narrower and the white mirror on P10 broader. The tips on fresh primaries are larger in adult birds.
• The tail may show small black spots on the tail-feathers.

As can be expected, there is no surprising moult going on in sub-adult birds, this time of the year. The average adult michahellis finishes primary moult by the end of October. By January, the outer primaries may show slight wear already. The winter head streaking, which was obvious and concentrated on the ear-coverts, around the eye and up to the crown by September and October, has been worn away by mid winter, leaving the snow white appearance as in adult michahellis.

For details on differences between michahellis and cachinnans, see e.g. the article by R. Klein & D. Gruber in Limicola, April 1997.

michahellis at Le Portel, NW France:

Le Portel and the near surrounding do not hold large colonies of Yellow-legged Gulls. Numbers of sub-adult Yellow-legged Gulls in NW France are low in winter. At the landfill of Dannes, near Le Portel, large mixed flocks of mainly Herring Gulls (1,000's) from NW and N Europe can be found including adult and sub-adult Yellow-legged Gulls (few tens in January 2002). By March, many adult Yellow-legged Gulls and with them the near adults return to the breeding grounds. The breeding season starts early for this species which breeds in southern Europe.

Photo 8645: Michahellis 4cy, January 04 2002, Le Portel, NW France.

A sub- adult michahellis in 4cy as can be told by the very small white tips on the relatively fresh outer primaries and the vermiculated pattern in the centres of the lower tertials. The white tip on P10 doesn't merge with the mirror but is separated by a broad sub-terminal band and even P5 shows a broad black patch.