Yellow-legged Gull - Larus michahellis

(last update: May 16, 2011)

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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.

L. michahellis: 1cy August

General description:

Yellow-legged Gulls L.michahellis, which breed in southern Europe / the Mediterranean have a significant earlier breeding season than the large gulls breeding in western and northern Europe, Herring Gulls (HG) argenteus & argentatus and Lesser Black-backed Gulls (LBBG) graellsii & intermedius). As a result, most juvenile YLG's show more worn plumages than northern relatives by August (on average). Geographical latitude of breeding grounds probably is the main reason for these differences in feather conditions, but there may be many other aspects involved as well, like e.g. exposure to severe summer light condition.

 

Subsequently, the average moult timing to 1st winter plumage commences earlier in the season (from late July-early August) than in LBBG and HG. By late August, almost all michahellis in the Calais Region, NW France already moult in second generation feathers. The mantle, scapulars and sometimes median covert, a few lesser coverts and tertials are involved. 
Herring Gulls with abraded fringes in the coverts and the same moult stage as michahellis are extremely rare, but some Lesser Black-backed Gulls also acquire new wing-coverts as early as August. However, in most cases the condition of the old feathers is different: michahellis have retarded feathers (the fringes of the feathers more abraded), while in graellsii the coverts are generally fresher. Of course it's interesting to find out how southern populations of graellsii adapt or change the egg-laying date in the near future now they expand their breeding area in France and further south.

Wing-covert moult in michahellis

The moult of the wing-coverts in michahellis may start in late July in a few individuals (see for details the tables presented in the July section). In the last week of August we scored moult stage in Boulogne-sur-Mer (NW France) in a group of 22 first calendar year (1cy) michahellis: 4 individuals (18%) had started the wing-covert moult (involving the median and lesser coverts). Late August, the most advanced individual showed c. 80% renewed median and greater coverts. Approximately 20% of the lesser coverts were moulted and the upper three tertials were missing. 

Most michahellis start moulting the wing-coverts in September and throughout the winter months wing-covert moult continues. About 80% of 1st winter michahellis will show at least some moulted wing-coverts in spring next season (by then in 2cy).
The first birds with a 90-100% wing-covert moult score (all visible wing coverts replaced by second generation feathers) can be found as early as September. We have limited experience with "late winter covert score" (by then 2cy michahellis in spring), but we estimate less than 10% of michahellis to show all the visible coverts new. Probably, at least some wing-coverts will not be shed in 1st winter and remain juvenile feathers until spring next season, when the complete moult-cyclus starts.

 

Table

 

Juvenile michahellis moult score Autumn 2001 the Netherlands

  new mantle new scapulars new coverts new tertials  
  yes no yes no yes no yes no n =
31 Aug 7 0 7 0 1 6 3 4 7
01 Sept 4 0 4 0 1 3 0 4 4
03 Sept 4 0 4 0 4 0 2 2 4
11 Sept 1 0 1 0 1 0 1 0 1
16 Sept - - 1 0 - - - - 1
28 Sept 1 0 1 0 - - - - 1
11 Oct 11 0 11 0 7 4 8 3 11
16 Oct 1 0 1 0 1 0 1 0 1
22 Oct 7 0 7 0 3 4 - - 7
Notes:
1) Yes means: active moult started; bird shed at least one feather of this tract, but some advanced birds may show several second generation feathers already.  
2) All observations at Maasvlakte, except 16 Sept (Bergen op Zoom) & 22 Oct (Westkapelle).

 

 

 

juvenile michahellis in August. (83051 bytes)michahellisM025982 1cy August 27 2012, Katwijk, the Netherlands.
Ringed in Switzerland.
juvenile michahellis in August. (83051 bytes)michahellisM015348 1cy August 08 2003, Boulogne/Mer, France.
Ringed in Switzerland.
juvenile michahellis in August.  (103191 bytes)michahellis 15Y 1cy August 12 2004, Westkapelle, the Netherlands (51.33N, 03.25E).
juvenile michahellis in August. (92854 bytes)Photo 20: michahellis 1cy August 12 2006, IJmuiden, the Netherlands.

juvenile michahellis in August. (92854 bytes)Photo 21: michahellis 1cy August 12 2006, IJmuiden, the Netherlands.

juvenile michahellis in August. (92854 bytes)Photo 7245: michahellis 1cy August 08 2003, Boulogne/Mer, France.
juvenile michahellis in August. (64795 bytes)Photo 7386: michahellis 1cy August 10 2003, Boulogne/Mer, France.
juvenile michahellis in August. (63948 bytes)Photo 7393: michahellis 1cy August 10 2003, Boulogne/Mer, France.
juvenile michahellis in August. (77546 bytes)Photo 7709: michahellis 1cy August 11 2003, Boulogne/Mer, France.
juvenile michahellis in August.Photo 1: Yellow-legged Gull 1cy August 25 2000, Le Portel / Boulogne-sur-Mer, France.
juvenile michahellis in August.Photo 2: Yellow-legged Gull 1cy August 25 2000, Le Portel / Boulogne-sur-Mer, France.
juvenile michahellis in August.Photo 3: Yellow-legged Gull 1cy August 25 2000, Le Portel / Boulogne-sur-Mer, France.
juvenile michahellis in August. (79150 bytes)Photo 4: Yellow-legged Gull 1cy August 25 2000, Le Portel / Boulogne-sur-Mer, France.
juvenile michahellis in August. (105128 bytes)Photo 5: Yellow-legged Gull 1cy August 22 2000, Le Portel / Boulogne-sur-Mer, France.
juvenile michahellis in August. (82476 bytes)Photo 6: Yellow-legged Gull 1cy August 16 2000, Bergen op Zoom, the Netherlands.
juvenile michahellis in August. Photo 7: Yellow-legged Gull 1cy August 25 2000, Le Portel - Boulogne/Mer, France.
juvenile michahellis in August. Photo 8: Yellow-legged Gull 1cy August 24 2000, Etaples, France.
juvenile michahellis in August. Photo 9: Yellow-legged Gull 1cy August 24 2000, Le Portel / Boulogne-sur-Mer, France.
juvenile michahellis in August. Photo 10: Yellow-legged Gull 1cy August 25 2000, Le Portel / Boulogne-sur-Mer, France.
juvenile michahellis in August. Photo 11: Yellow-legged Gull 1cy August 24 2000, Etaples, France.
juvenile michahellis in August. Photo 12: Yellow-legged Gull 1cy August 24 2000, Etaples, France.
juvenile michahellis in August. (107058 bytes)Photo 13: Yellow-legged Gull 1cy August 24 2000, Etaples, France.
juvenile michahellis in August. (96352 bytes)Photo 14: Yellow-legged Gull 1cy August 22 2000, Le Portel / Boulogne-sur-Mer, France.
juvenile michahellis in August. (102216 bytes)Photo 15: Yellow-legged Gull 1cy August 21 2000, Le Portel / Boulogne-sur-Mer, France.