Yellow-legged Gull - Larus michahellis

(last update: October 08 2013)

Delfín González
Gabriel Martín
Antonio Gutierrez
Amir Ben Dov
Mars Muusse

Yellow-legged Gull michahellis 2CY, November 15 2003, Westkapelle, the Netherlands (51.33N-03.25E).

All summer, 2CY michahellis are in a complete moult, replacing all feathers, which eventually will bring birds in so-called "second winter" plumage by October. After completion, the head will show limited neat fine streaking and the under-parts and rump turn pale, with some mottled brown at the flanks. 
From early April, the inner primaries are shed and new second generation primaries grown in. On average, 2CY michahellis shed the last juvenile primary (P10) by the first week of August. The majority of michahellis complete the primary moult by the first week of October, when the new second generation P10 is fully grown. The new primaries are dark with a tiny pale tip on the fresh flight-feathers. In michahellis, second generation primaries show some contrast between outer and inner primaries: the three inner primaries show a pale inner-web and brownish outer-web (the black shaft-streak well visible), while the outer primaries have the outer-web blackish brown and the pale greyish brown inner-web still visible at P7. 
The under-wing is largely pale with brown lesser under-wing coverts and brown lines running over the tips of the median coverts. The second generation tail-feathers show a clear-cut wedge-shaped blackish tail-band with only isolated blackish markings on the white basal half of the central rectrices. The outer tail-feathers normally show no isolated black markings and in general the outer-webs are often clean white except the sub-terminal band. The rump is largely white. The iris is pale brown. The bill shows a pale pinkish base and often the very tip is translucent white. The legs are salmon-pink with a yellow hue.
At the end of the complete moult, a partial moult takes place in September and October. In this partial moult, 2CY birds normally include some feathers, which were replaced first in line in the complete moult of last summer (in May): upper tertials, median coverts, inner greater coverts and randomly some lower lesser coverts.

The image below shows an average bird in November. The head and under-parts show streaking and mottling and the bill looks immature as well. Primary P10 is fully grown and all the secondaries and rectrices are second generation and complete. Hence, the complete moult has ended, as can be seen in most late-September 2CY michahellis. After this complete moult, a partial moult has included three upper tertials and some wing-coverts: greater coverts #2, #4-5; median coverts #1-6 and #8-14, with #14 the last visible; 7 lower lesser coverts and a few inner lesser coverts. Most of the scapulars are grey with an obvious shaft-streak.