Yellow-legged Gull- Geelpootmeeuw (L. michahellis): 1cy September

(last update: 18 oktober 2004)

ORG SITE

YLG 1cy May
YLG 1cy June
YLG 1cy July
YLG 1cy August
YLG 1cy September
YLG 1cy October
YLG 1cy November
YLG 1cy December

YLG 2cy January
YLG 2cy February
YLG 2cy March
YLG 2cy April
YLG 2cy May
YLG 2cy June
YLG 2cy July
YLG 2cy August
YLG 2cy September
YLG 2cy October
YLG 2cy November
YLG 2cy December

YLG 3cy January
YLG 3cy February
YLG 3cy March
YLG 3cy April
YLG 3cy May
YLG 3cy June
YLG 3cy July
YLG 3cy August
YLG 3cy September
YLG 3cy October
YLG 3cy November
YLG 3cy December

YLG sub-ad Jan.
YLG sub-ad Feb.
YLG sub-ad March
YLG sub-ad April
YLG sub-ad May
YLG sub-ad June
YLG sub-ad July
YLG sub-ad Aug.
YLG sub-ad Sept.
YLG sub-ad Oct.
YLG sub-ad Nov.
YLG sub-ad Dec.

YLG adult January
YLG adult February
YLG adult March
YLG adult April
YLG adult May
YLG adult June
YLG adult July
YLG adult August
YLG adult September
YLG adult October
YLG adult November
YLG adult 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.

General description:

By September, the vast majority of 1cy michahellis has rather worn fringes at the juvenile feathers and the brown centres are already somewhat bleached. By this month, most of the mantle feathers and upper scapulars have been moulted more than a month ago and the buffish / gingery centres of the second generation feathers start to turn paler, almost white. Hence, these scapulars show almost white based centres, strongly contrasting with the dark anchor or barred pattern on the lower and upper scapulars. 

The majority of juvenile W European Herring Gulls and Lesser Black-back-backed Gulls have left the colonies as well and many of them appear slightly worn; resembling Yellow-legged Gulls. The clues to separate resting juvenile michahellis and graellsii become less reliable, but still, best characteristics in September are the inner primary pattern, tail-pattern and condition / moult-stage of second generation tertials and coverts.

Moult stage and pace of the scapulars

Throughout September, the mantle and scapulars are almost completely replaced by second generation feathers. Below, a table is presented with scapular moult scores of 20 juvenile michahellis in the Calais region, NW France. The vast majority of the birds have the upper scapulars moulted to second generation feathers, with only a few smaller upper scapulars remaining juvenile (therefore a moult score of the fully 100% only occurs in a few individuals, but within the upper scapular moult-class 75-100%, most birds have moulted over 90% of the visible upper scapulars). 

By the end of the month September, a few moult gaps and single retarded juvenile feathers may still be present in the outer upper scapulars. The clearly visible lower scapulars, which are moulted later than the upper scapulars, may still show the brownish or buffish base between the dark bars or anchor pattern in the second generation feathers. 

As can be seen in the images, these fresh second generation feathers have a broad white fringe. The feathers which were moulted longer ago have the base turned paler and show contrasting brown/black - white feathers. Some second generation scapulars already show wear in the fringes by September. Those feathers can be found in the rear upper scapulars and the rear upper lower scapulars. 

By the end of the month, there may still be moult gaps in the lower scapulars, especially the central and rear feathers in the lowest row of lower scapulars (the feathers covering the scapular coverts). Moult scores in the first week of October reveals that the rear feathers in the lowest row of lower scapulars are still present and juvenile in the majority of the 1cy michahellis.

Moult stage and pace of the wing-coverts and tertials

The covert moult stage and tertial moult stage may vary to a large extend. Some birds still show a complete juvenile wing, with worn covert fringes (especially the inner coverts) and juvenile tertials. These 1cy michahellis birds strongly resemble graellsii when the wings are folded and the bird rests. By the end of the month, about 25% of the 1cy michahellis have all the wing-coverts and tertials still juvenile. Some of these juvenile birds may still start the partial moult by late September, as the figures slightly drop by October. Wing-covert scores from late October show that only 15-20% of the juvenile birds still have all the wing-coverts juvenile. Over 80% have replaced at least a single wing-covert to second generation feathers.

Most 1cy birds show advanced wing-covert moult, normally including the inner medians, the inner lower lessers and the inner greater coverts. The wing-covert moult is often most advanced in the median covert row, which can consist of second generation coverts for over 50% (most of the visible median coverts in a folded wing). Less than 50% of 1cy birds start moulting the tertials in September, often starting with the upper two tertials or with the third tertial. The juvenile tertials are plain brown centred and the fringes are almost completely worn away, leaving a protruding shaft streak. By early October however, many birds shed the upper tertials and figures from late October show replaced upper tertials in the majority of the birds.

Replacement of the tiny lesser coverts is hard to establish in the field and most of the time impossible unless close range images are obtained or the bird is examined in the hand. In the table below, "missing lesser wing-coverts" must be read as "feathers missing or growing". Still, this doesn't fully eliminate the problem of judging the stage of moult in these feathers, as it may remain debatable whether a feather is fully grown or not.

Moult stage and pace of the rectrices

The small sample of birds in the table below didn't include any juvenile michahellis moulting the tail-feathers. A sample from the first week of October included several birds with moulted rectrices which confirms the general idea that at least a small minority of 1cy michahellis includes tail-feather replacement in the post-juvenile moult from October onwards. In any moderate group of first calendar year michahellis, birds can be found moulting the tail-feathers by October (see the October section for tables). The exact extend of this moult is still not known, but in spring, 2cy michahellis with second generation tail-feathers can be seen regularly (even birds with the tail completely moulted). Next year, more research will be executed on this topic.

Movements

The majority of michahellis in NW France arrive from SW origins, the colonies from Marseille and the Mediterranean coast towards NE Spain, Italy, Switzerland and the German Rhine colony. Some birds must have origins further south, as the ring recoveries of blue ringed Sardinian birds and black ringed NE Spanish birds indicate.

Tables

Moult score of twenty juvenile michahellis, September 20-22 2002, Boulogne-sur-Mer / Etaples, NW France.

ind: tertials gr cov med cov low les cov les cov low scaps upp scaps
1. old old old old old 1-25% 25-50%
2. old old old old old 25-50% 50-75%
3. old old old old old 75-100% 75-100%
4. old old old old old 75-100% 75-100%
5. old old old old old 75-100% 100%
6. old old old 3 miss old 75-100% 100%
7. old old 1 miss 1 miss 2 miss 50-75% 75-100%
8. old old 7 new 3 new old 75-100% 100%
9. old 1 miss 3 new, 2 miss 2 new, 5 miss 13 new, 10 miss 75-100% 75-100%
10. old 2 miss 5 miss 3 miss 2 miss 25-50% 100%
11. old 2 new 3 new 3 new old 75-100% 100%
12. 1 new old old old old 75-100% 100%
13. 1 miss old old 6 miss old 75-100% 75-100%
14. 1 miss old old 1 new 14 new 75-100% 100%
15. 1 miss 1 new 6 new 4 new 2 new 50-75% 75-100%
16. 1 miss 2 new 5 new 5 new 2 new 75-100% 100%
17. 2 miss 4 new, 2 miss 10 new, 3 miss 3 new, 6 miss 10 new 5-10 miss 75-100% 100%
18. 2 miss 1 new 5 new, 5 miss 2 new, 2 miss 1 new, 5-10 miss 75-100% 75-100%
19. 2 new 3 new 5 new 5 miss 4 new 75-100% 75-100%
20. 2 new 2 new 9 new, 1 miss 4 new, 2 miss 4 new, 3 miss 75-100% 100%
Notes: 
number: (amount) of replaced tertials, wing-coverts and scapulars. 
Feather tracts:
gr cov = greater coverts; med cov = median coverts; low les cov = lower lesser coverts; les cov = lesser coverts; low scaps = lower scapulars; upp scaps = upper scapulars. For details on feather tracts, see the topography page.
new: feather fully grown; 
miss: feather missing or growing, not fully grown.

 

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 2001, Maasvlakte 7 0 7 0 1 6 3 4 7
01 Sept 2001, Maasvlakte 4 0 4 0 1 3 0 4 4
03 Sept 2001, Maasvlakte 4 0 4 0 4 0 2 2 4
11 Sept 2001, Maasvlakte 1 0 1 0 1 0 1 0 1
16 Sept 2001, Bergen op Zoom - - 1 0 - - - - 1
28 Sept 2001, Maasvlakte 1 0 1 0 - - - - 1
11 Oct 2001, Maasvlakte 11 0 11 0 7 4 8 3 11
16 Oct 2001, Maasvlakte 1 0 1 0 1 0 1 0 1
22 Oct 2001, Westkapelle 7 0 7 0 3 4 - - 7
Notes:
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.

 

1cy L. michahellis in September, ringed in S France. (81733 bytes)michahellis CC-9273 September 01 2006, IJmuiden, the Netherlands.

 

1cy L. michahellis in September, ringed in S France. (81733 bytes)michahellis332Z, September 16 2002, Scheveningen, the Netherlands. From July 13 into September, a 1cy michahellis is present in SW Netherlands. Ringed as pullus near Marseille, S France.
1cy L. michahellis in September, ringed in Italy. (62225 bytes)ILZB YLG (L. michahellis) 1cy, September 20 2002, Boulogne/Mer, France.
1cy L. michahellis in September, ringed in Italy. (52829 bytes)I153 YLG (L. michahellis) 1cy, September 28 2004, Westkapelle, the Netherlands. Photo Pim Wolf. 
1cy L. michahellis in September, ringed in Italy. (49714 bytes)I013 YLG (L. michahellis) 1cy, September 13 2003, IJmuiden, the Netherlands. Photo Kees Verbeek. 
1cy argenteus in November, ringed in Belgium. (25637 bytes)michahellis 97Y 1cy November 02 2008, Westkapelle, the Netherlands. Picture: Pim Wolf..
1cy L. michahellis in September. (75894 bytes)Photo 01: YLG (L. michahellis) 1cy, September 02 2006, IJmuiden, the Netherlands.
1cy L. michahellis in September. (75894 bytes)Photo 02: YLG (L. michahellis) 1cy, September 02 2006, IJmuiden, the Netherlands.
1cy L. michahellis in September. (75894 bytes)Photo 4673: YLG (L. michahellis) 1cy, September 20 2002, Le Portel, France.
1cy L. michahellis in September. (80331 bytes)Photo 4677: YLG (L. michahellis) 1cy, September 20 2002, Le Portel, France.
1cy L. michahellis in September. (64455 bytes)Photo 4682: YLG (L. michahellis) 1cy, September 20 2002, Le Portel, France.
1cy L. michahellis in September. (66607 bytes)Photo 4690: YLG (L. michahellis) 1cy, September 20 2002, Le Portel, France.
1cy L. michahellis in September. (70727 bytes)Photo 4691: YLG (L. michahellis) 1cy, September 20 2002, Boulogne-sur-Mer, France.
1cy L. michahellis in September. (54374 bytes)Photo 4749: YLG (L. michahellis) 1cy, September 21 2002, Dannes - Le Portel, France.
1cy L. michahellis in September. (75180 bytes)Photo 4774: YLG (L. michahellis) 1cy, September 21 2002, Dannes - Le Portel, France.
1cy L. michahellis in September. (70685 bytes)Photo 4788: YLG (L. michahellis) 1cy, September 21 2002, Dannes - Le Portel, France.
1cy L. michahellis in September. (59557 bytes)Photo 4986: YLG (L. michahellis) 1cy, September 22 2002, Le Portel, France.
1cy L. michahellis in September. (74375 bytes)Photo 6495: YLG (L. michahellis) 1cy, September 30 2001, Dannes - Le Portel, France.
1cy L. michahellis in September. (97915 bytes)Photo 6509: YLG (L. michahellis) 1cy, September 30 2001, Dannes - Le Portel, France.
1cy L. michahellis in September. (77586 bytes)Photo 6516: YLG (L. michahellis) 1cy, September 30 2001, Dannes - Le Portel, France.