Yellow-legged Gull - Larus michahellis

(last update: October 08 2013)

Coordinators:
Delfín González
Gabriel Martín
Antonio Gutierrez
Amir Ben Dov
Mars Muusse

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Larus michahellis - 2CY January

This website deals with the Yellow-legged Gull taxon michahellis, which is a common migrant from July to December in NW Europe. After extensive expansion of the breeding population during the last three decades, it nowadays can be found breeding in Belgium, the Netherlands and Britain in mixed couples with both Herring Gull (argenteus) and Lesser Black-backed Gull (graellsii). There are subtle differences between the populations from the Mediterranean, Atlantic coast of Portugal and Morocco and from the islands in the Atlantic. Most pronounced differences can be found in the taxon atlantis, now regarded as full species by some authors and birds along the Atlantic coast of the Iberian peninsular: lusitanius. Both atlantis and lusitanius are treated in their own sections on this website.

General description:

By mid-winter, many 2CY michahellis continue the post-juvenile moult in the wing-coverts and the tertials. Year 2002, we checked limited numbers of 2CY michahellis as Etaples in NW France holds only a few 10's of birds. More information on the Etaples-site can be found on the Le Portel Page).

A very few January 2CY birds show third generation scapulars, which are grey-based with an ill-defined brown or black pattern. The head normally appears smudgy, with a dark patch around the eye, extending to the nape. The hind-neck has a contrasting neck-collar, running down along the side-breast towards the flanks and belly. An example can be found in the first image, showing a strong male michahellis with the head rather pale.

Remiges & rectrices moult stage and pace:

By January, replacement of the primaries and rectrices hasn't started in 2CY michahellis. The first primaries are only dropped by mid-April. About 5% of michahellis includes tail-feathers in the partial moult in autumn and may show second generation rectrices by January. At this moment, it's not completely clear whether this moult in the rectrices continues throughout the wintering months, as limited data are not sufficient to support the hypothesis.

Wing-covert moult stage and pace:

In several sections of 1CY michahellis it's mentioned that birds include wing-coverts in the post-juvenile moult (unlike argentatus / argenteus where this post-juvenile moult is confined to the scapulars, and only seldom  single wing-coverts are included). The general conclusion is that between September (in first calendar year) and January (in second calendar year) the moult is not suspended but replacement progresses in a slow pace. Several pictures in this section show birds which are still actively moulting the coverts, with growing or missing coverts. The first image shows growing greater coverts and the fourth image shows a bird with missing coverts.
However, there are still 2CY birds which have all the wing-coverts and tertials juvenile.

Mantle & scapular moult stage and pace:

By January, the second generation feathers in the lowest row of lower scapulars are finally visible; these lowest scapulars are moulted last in line. The moult to third generation scapulars may start in some birds, although most of these birds will only replace a single or a few lower upper scapulars in January at Le Portel, NW France. Nonetheless, missing lower upper scapulars is not uncommon in January in 2CY birds. The fresh third generation scapulars show anchor an bar patterns not unlike the second generation feathers, although these third generation feathers are often grey-based. Later in the season, from April onwards the third generation feathers may look more adult-like, with the bases extensive grey and the pattern reduced to an ill-defined dark shaft-streak or even completely plain grey (although these third generation feathers often appear slightly browner towards the edges and tip). The last lower scapulars, which can be found in the lowest row, often the rear feathers on the back, are moulted to second generation. Subsequently, in the scapulars simultaneous moult can be found to second generation feathers (in the lower scapulars) and to third generation feathers (in the upper scapulars).