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 June

General description:

Identification of juvenile Yellow-legged Gulls isn't always easy, but with a combination of characteristics, positive identification must be possible in almost all of them. Within the region (NW Europe), most confusion may arise with juvenile Herring Gulls argentatus and argenteus and juvenile Lesser Black-backed Gulls graellsii. Juvenile white-headed gulls from SE Europe, e.g. Steppe Gull cachinnans, Baraba Gull barabensis, and Armenian Gull armenicusare other candidates for causing problems. An excellent article about differences between michahellis and cachinnans  has been written by R. Klein & D. Gruber in Limicola, April 1997.


Some general clues for identifying michahellis in July

  • Rather dark inner primaries compared to argenteus and cachinnans, the window is rather ill-defined (see image 5545), but the inner primaries are not all dark as in most graellsii;

  • Normally the tertials show an all dark tertial-centre with a smooth white fringe as in graellsii (see image 5699). The tertials are normally not as obviously notched as in argenteus. Michahellis may show a broad well-defined pale bar between the sub-terminal band and the dark centre (a transversal bar), but some variations of the pattern occurs (see also image 5707);

  • Pale under-parts: normally a streaked breast-band contrasts with the white chin and the pale belly (see image 5698). The under-parts in argenteus are overall warm coloured, more yellow-brown. In fresh juvenile graellsii the brown sides of the neck are often connected to the brown ear-coverts and the brown runs from the crown to the breast, forming a larger all brown patch;

  • Greater coverts often lack the 'piano' pattern in michahellis; a pattern obvious in argenteus (see image 5699). The outermost greater coverts become gradually darker, with only a thin white fringe running all the way to the base. Nevertheless, in some michahellis the greater covert pattern may resemble that of argenteus. Juvenile cachinnans in July normally still show a fresh broad creamy-white tip to the median coverts, creating what might be called a pale bar at the folded wing, when observed from a distance. Michahellis normally lacks this bar and by July, the median coverts may appear slightly worn at the tips already, especially the innermost medians;

  • Under-wings are dark clouded or with a vermiculate pattern, much darker than the average cachinnans (see image 15);

  • Shins are often pale, not contrasting with the rest of the legs (see image 5578); the shins are often dark in graellsii;

  • The tail-band is broadest at the centre, becoming smaller at outer tail feathers, so obviously different from the broad dark tail-band commonly seen in graellsii and argenteus (see image 11);

  • The upper-parts are not rich yellow-coloured as in argenteus, but rather cold pale brown (see e.g. image 5545), with white fringes and brown centres to the scapulars and coverts. Contrary cachinnans, michahellis normally lacks the neat post stamp fringes in the lower scapulars which may be very obvious in cachinnans. By July, michahellis actively moult upper and upper lower scapulars and the juvenile lower scapulars have abraded fringes (for terms used: see Topography section);

  • Moult in the upper-parts starts early in the season in michahellis, as can be seen in many images. Michahellis has early fledglings, consequently has more untidy looking plumage in mid-summer juveniles.


Juvenile michahellis by the end of July


One of the most striking characteristics of 1cy michahellis is it's quick moult. As early as the end of July, many scapulars, mantle feathers and sometimes tertials or  wing-coverts are shed or replaced by post-juvenile feathers. From 26 to 30 July 2001, we described 59 juvenile michahellis at NW France: at Etaples (Le Tourquet) and at Le Portel (Boulogne-sur-Mer: 50.42 N, 1.34 E). All present juveniles were included. Over the period, we may have described (incidentally) the same bird when we visited fixed locations (but we kept those counts separated), and the general conclusions on bird present at this location presented here will stand, supported by the images shown at this page.


The general idea is that michahellis, after leaving the colonies in June or July, quickly starts the post-juvenile moult. The first signs of moult are usually detected in the upper scapulars and mantlefeathers, followed by other parts of the body-feathers and sometimes upperwingcoverts and/or tertials. 


The retained juvenile feathers are normally very fresh or only very slightly abraded. Given this good quality of the feathers during this month, it is not likely that these feathers are replaced for maintaining primary plumage functions (i.e. protective and locomotoric) at the moment of renewal. It is likely that the post-juvenile moult has been initiated in order to optimize primary plumage functions during winter.   





Juvenile michahellis moult score July 10-11 2002 Etaples & Le Portel (50.42 N, 1.34 E )
no scapulars missing 5
1-5 scapulars missing 10
6-10 scapulars missing 2*
* including 1 bird with tertial #1 missing and 1 individual already growing new scapulars.


The small survey in the period July 26-30 2001, showed only one single bird in complete juvenile plumage, i.e. not actively moulting scapulars and mantle. The conclusion is that the vast majority (> 90%) moult scapulars by the end of July and over 25% moult wing-coverts. Only a few (< 5%) had shed tertials.


Juvenile michahellis moult score July 26-30 2001 Etaples & Le Portel (50.42 N, 1.34 E )
  new mantle new scapulars new coverts new tertials  
  yes no yes no yes no yes no  
Etaples 25 0 22 3 4 21 0 25 n = 25
Le Portel 33 1 33 1 12 22 2 32 n = 34

Yes means: active moult started; bird shed at least one feather of this tract, but some advanced birds may show several 2nd generation feathers already.
Etaples count included some distant birds, making mantle score more difficult. Le Portel counts were at close range.
Some birds were behind in moult, but nevertheless they could show extensive wear, especially in the inner coverts, tertials and lower rear scapulars.
Scapular moult often starts at the inner 2 median coverts. The next 2 or 3 are left juvenile, after which a few central feathers are shed. In the greater coverts, the strategy may be similar, but we only saw juveniles which had shed the innermost greater coverts.
Only 2 juvenile michahellis were moulting tertials.


In the same period a large gull resting place was visited near Venice, Italy. Out of 51 juvenile michahellis, only 1 didn't start moulting mantle feathers, 3 out of 51 didn't start moulting scapulars. These figures are perfectly in line with the survey from NW France. Regarding the moult in the coverts and tertials, birds in Italy are slightly ahead of the birds in NW France.


Lignano, Venice, Italy (45.28N-12.23E):  July 27 and 29th 2001. juvenile michahellis, n = 51. The results of this survey are much in line with the observation made in NW France.
  mantle scaps  gc**  mc/lc**  tertials
0% 1 3 none* 30 none* 35 none* 45
1-50% 30 48 inner* 12 inner* 10 #1* 3
50-100% 20 0 outer* 8 outer* 6 #1-#2* 2
  in+outer* 1    
*: none = no moult, #1 = upper tertial, #1-#2 = upper two tertials
**: gc = greater coverts, mc/lc = median and lesser coverts aggregated.


adult michahellis in April. (61415 bytes) michahellis 1cy U1KF June 05 2010, Tel Aviv University - Zool. Garden, Israel. Picture: Amir Ben Dov.
adult michahellis in April. (61415 bytes) michahellis 1cy U9BH July 10 2010, Tel Aviv University - Zool. Garden, Israel. Picture: Amir Ben Dov.
2256mich332z.jpg (71315 bytes)michahellis 1cy 332Z, July 13 2002, Dintelhaven - Maasvlakte, the Netherlands. Already a few scapulars moulted in the lowest row of upper scapulars. Compare the colour of the feather-centres with Lesser Black-backed Gull. Ringed near Marseille, S France.
1cy michahellis.mihahellis G6.06 1cy July 28 2010, Malaga, Spain.
Ringed in Malaga. Picture: G. Martin.
2cy michahellis in August, ringed in Switzerland.michahellis 1cy July 28 2010, Malaga, Spain.
Picture: G. Martin.
2397.jpg (66215 bytes)michahellis 1cy, July 14 2002, Dintelhaven - Maasvlakte, the Netherlands. Compare the Yellow-legged with the Herring Gull in front.
adult michahellis in April. (61415 bytes) michahellis 1cy July 09 2011, Tel Aviv University - Zool. Garden, Israel. Picture: Amir Ben Dov.
Chick from mixed nest armenicus x michahellis.
1865mich1cy.jpg (70109 bytes)michahellis 1cy, July 10 2002, Le Portel (France).
1895mich1cy.jpg (73960 bytes)michahellis 1cy, July 10 2002, Le Portel (France).

1905mich1cy.jpg (74886 bytes)michahellis 1cy, July 10 2002, Le Portel (France).

5530.jpg (96794 bytes)michahellis 1cy, July 26 2001, Le Portel (France). Already 7 scapulars moulted, 4 median and 1 greater coverts missing and active moult in the mantle.
5545.jpg (100466 bytes)michahellis 1cy, July 26 2001, Le Portel (France). Note the breast band.
5698.jpg (107891 bytes)michahellis juveniles, July 29 2001, Dannes - Le Portel (France).
5707.jpg (110448 bytes)michahellis 1cy, July 30 2001, Le Portel (France). The most advanced juvenile encountered.
5547.jpg (96519 bytes)michahellis 1cy, July 26 2001, Le Portel (France). 1 greater covert missing and 1 new, 1 median new, 2 missing and 2 feathers growing. Active moult in mantle and scapulars.
5578.jpg (93479 bytes)michahellis 1cy, July 27 2001, Le Portel (France). Somewhat different in not showing a clear breast band but note the pale shins.
5659.jpg (106489 bytes)michahellis 1cy, July 28 2001, Le Portel (France). A few scapulars missing. This is an example of the most 'extreme' wear we came across in juveniles.
5699.jpg (106239 bytes)michahellis 1cy, July 29 2001, Dannes - Le Portel (France).Note the dark shins, which are in most michahellis pale.
5711.jpg (94384 bytes)michahellis juveniles, July 30 2001, Le Portel (France). Just a few upper scapulars missing. Innermost greater covert missing too.
5723.jpg (107244 bytes)michahellis juveniles, July 30 2001, Le Portel (France). Resting bird: 9 scaps new, 5 missing. Standing bird: 9 scaps new, innermost greater covert missing and tertial #4 growing and just visible.