Yellow-legged
Gull - Larus michahellis
(last update: October 08 2013)
Coordinators:
Delfín González
Gabriel Martín
Antonio Gutierrez
Amir Ben Dov
Mars Muusse
Larus michahellis - 1CY December
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 December, 1CY michahellis shows more or less the same moult stage as birds from November. Active moult is nearly completely suspended now winter starts. Remarkably, in mid winter, the majority of michahellis from SW Netherlands and Le Portel (NW France) still show completely juvenile wing-coverts (but sample size is insufficient to draw any conclusions). This contradicts with the figures from July - September, so different individuals (and even different populations?) may be involved throughout the months. On some locations in the Netherlands, like landfills, inland gravel pits along the river Meuse and along the coast (like the Maasvlakte, near the port of Rotterdam) small groups can be found daily.
Mid-winter identification:
Identification of 1CY Yellow-legged Gull
is rather straightforward in birds with moulted wing-coverts and tertials,
although some 1CY cachinnans may look pretty similar, especially
when males are involved. To compare these plumages, have a look at the 1CY cachinnans section. Yellow-legged Gull has extensive moult
in the under-parts by December, with the second generation head already
turning white in some individuals. The 1CY partial moult (post-juvenile
moult) in the under-parts includes the head, neck, breast, belly and
flanks. The under-tail coverts are normally excluded from this partial
moult.
The mantle and scapulars consist of second generation feathers, which are
slightly worn at the fringes in the upper scapular region. These feathers
were moulted late July and in August, hence are already more than four
months old. In the lowest row of the scapulars, the recently moulted
feathers have a neat fringe but the buffish hue on the centres start to
fade away. In some 1CY michahellis, the next moult in the upper scapulars
takes place, with feathers now replaced for the second time: moult to
third generation.
Normally, best clues for 1CY michahellis:
- strong and powerful bird. Strong breast, large bird, especially males.
- heavy bill with an obvious gonydeal angle.
- angular head with sloped forehead.
- advanced moult stage in under-parts and scapulars.
- ill-defined window on the inner primaries confined to the inner-webs of the primaries.
- wedge-shaped tail-band, narrow on the outer rectrices (R6), where almost completely reduced to the inner-web of R6.
- dark outer greater coverts with the white fringe not reaching the base of the feather on the outermost greater coverts.
Moult stage and pace:
All 1CY michahellis have shed and replaced the juvenile feathers in the scapulars and mantle feathers. In turn the mantle and scapulars feathers are completely second generation. The ordinary pattern is a pale based centre with dark bars or an anchor pattern.
The covert and tertial moult vary to a large extend at Etaples, with a remarkable high proportion of birds in January showing all the wing-coverts and tertials still juvenile (remarkable higher numbers than expected on the figures from October, where only 19-27% of the 1CY birds had all the wing-coverts and tertials juvenile). Year 2002, more research at this location has to be executed to confirm the first findings. An example of a bird with all the wing-coverts and tertials still juvenile can be seen in image 7990.
Other birds have various amount of replaced feathers in wing-coverts and tertials (as can be seen in image 7963). Limited data on moult doesn't allow us to draw any conclusions on the average 1CY michahellis moult stage by mid December.
Yellow-legged
Gull michahellis 1CY U1KF December 17 2010, Tel Aviv - University Garden, Israel. Picture: Amir Ben Dov.
Yellow-legged Gull michahellis U9KA 1CY, December 23 2012, Ashdod, Israel. Pictures: Amir Ben Dov.
Yellow-legged
Gull michahellis 1CY NTT8 December 23 2002, Amsterdam, the Netherlands
(52.21N 04.52E).
Yellow-legged Gull michahellis 1CY PACF December 30 2010, Tarragona, Spain. Picture: Albert Cama Torrel.
Yellow-legged
Gull lusitanius F434 1CY, December 03 2014, Portimão, Portugal. Picture: Maarten van Kleinwee.
Yellow-legged Gull michahellis 1CY ST07 December 17 2006, Crikvenica, Croatia (45.11 N 14.42 E). Picture: D. Štefančić.
Yellow-legged Gull michahellis HES M0xx396 1CY, December 30 2010, Dordrecht, the Netherlands. Picture: Albert de Jong.
Yellow-legged Gull michahellis 1CY 492H & 494H December 06 2010, Jakuševec landfill, Zagreb, Croatia. Picture: ringing team Luka Jurinovic.
Yellow-legged Gull michahellis 45AH 1CY, December
14 2014, Zagreb, Croatia. Photo: Mladen Ban.
Yellow-legged Gull michahellis 97AH 1CY, December
14 2014, Zagreb, Croatia. Photo: Mladen Ban.
Yellow-legged
Gull michahellis 1CY, December 21 2001,
Westkapelle, the Netherlands (51.33N,3.25E).
Yellow-legged
Gull michahellis 1CY, December 21
2001, Westkapelle, the Netherlands (51.33N,3.25E).