Yellow-legged Gull- Geelpootmeeuw (L. michahellis): 2cy July

(last update: 13 oktober 2004)

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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.

From July 26-30 2001 and from July 10-11 2002 we did small surveys on Yellow-legged Gulls at Le Portel (near Boulogne-sur-Mer) and Etaples (near Le Tourquet). In this survey, we scored moult-stages to determine timing of moult in primaries, wing-coverts, tail-feathers, secondaries and body-feathers. At this moment, this website will only enlarge upon the general characteristics and moult stage of michahellis by July. For details on differences between michahellis and cachinnans, see e.g. the article by R. Klein & D. Gruber in Limicola, April 1997. 

 

General description:

By July, primary moult is obvious as the outermost flight-feathers are dropped now and the birds look 'short-winged'. Most birds have the wing-coverts completely fresh and neat, as the gaps in the median and greater wing-covert rows have been closed. By the end of the month, many birds are still moulting lesser coverts in the upper row, which may be difficult to detect, covered by the lowest scapulars. Some birds still show old second generation feathers, which were included in the post-juvenile moult last autumn (see 1cy September & October). The inner median coverts which were moulted first in line in the complete moult two months ago, start to bleach already and loose the warm tones. The majority of 2cy michahellis is easily identified by (some) adult-like grey scapulars.

By July, 2cy michahellis in the last stage of the complete moult (second pre-basic moult) can be found commonly around the harbour of Etaples in NW France with 10's of birds in the direct surrounding of the fish-market and 100's of immature birds using the near landfill of Dannes to feed on.

Grey-based scapulars or barred scapulars:

The images on the right-hand side show 2cy michahellis, classified by their general appearance: the top birds are typical "barred individuals". The fresh wing-coverts and the fresh scapulars show a barred pattern. Just by this pattern, these birds look more immature than the birds in the bottom images.
The bottom images show 2cy michahellis which have grown in many fresh plain grey scapulars and some wing-coverts. Therefore they appear more adult-like, although the amount of replaced feathers is not necessarily larger than in the barred individuals of the top images. Its just the look: grey scapulars suggest maturity. Compare this barred individual with this more advanced looking individual; both 2cy michahellis from July.

Moult stage and pace of remiges and rectrices:

We have extensive surveys on primary moult stage of both 2cy michahellis and 2cy argenteus. The figures can be viewed in the tables and cross-tables below. We described 2cy birds in detail on six occasions at Etaples, Calais region Peter Adriaens kindly provided video footage to score primary moult stages in Croatian birds. Late July 2001, a visit was organized to Lignano, Italy, to score over 100 2cy michahellis on this location.

By 3rd July, 2cy michahellis from Croatia have an average 3.0 primaries left (n =n 27), i.e. P8-P10 still juvenile. During the month, the outer primaries are shed as well, with primary moult score of 2.2 (n = 45) and 2.3 (n = 48) remaining old primaries at Etaples, NW France by 10th July. By the end of July, 2cy michahellis has only one or two old juvenile primaries left, with one-third of the birds having dropped all primaries. 
Compared to argenteus, these michahellis figures show that the average gap in the primaries is larger in michahellis (the gap between new second generation primaries and retained old juvenile primaries). 

By early July, the average 2cy michahellis has P5 renewed and fully grown. By the end of the month this score has increased one primary, P6 fully grown by 28th July. The most advanced birds by late July show an obvious short wing, with P10 dropped and P7 already fully grown. One bird has P8 fully grown. Note the relatively low SD value (standard deviation) in these primary moult scores, which implies a small range of variation. 

The majority of 2cy michahellis have started the moult in the rectrices and the secondaries. As can be seen in previous sections, michahellis may moult rectrices in the partial moult in 1cy, but the complete moult in the tail-feathers is normally postponed until July; when the inner four primaries are grown, the moult in both secondaries and rectrices will start.

Moult stage and pace of wing-coverts:

In several sections of 1cy michahellis it's mentioned that birds include wing-coverts in the post-juvenile moult (unlike argentatus / argenteus where this post-juvenile moult is confined to the scapulars). To distinguish between 2cy birds which have still suspended moult (after the post-juvenile moult) and birds which have really started to replace wing-coverts, we separate between old second generation feathers and fresh second generation feathers in the April, May and June sections. This is much easier said than done, especially by May and June, when the old second generation feathers (required as early as late-August) and the juvenile wing-coverts may be extremely similar and abraded.
Its interesting to see that t
he wing-coverts, which were included in the post-juvenile moult are left out of the first stage of the complete moult in early summer. They are replaced at a later stage, after July in some individuals. This is nicely demonstrated by a Swiss metal-ringed michahellis Sempach 885629. The exact figures of such "stepping" moult sequences are hard to obtain, as birds which do drop these earlier moulted feathers are not recognized of course. 
However, irregular moult sequences are not found in the tertials, as in most birds, replacement in the tertials follows the ordinary sequence, from tertial #1 downwards.

The complete moult in the wing-coverts may start by April, with the majority of 2cy michahellis starting moult by early May. Except the difference in timing of moult, these new second generation feathers may show a different pattern than second generation feathers from the partial moult. Fresh second generation feathers moulted from April and May onwards appear 'less immature': the base colour of the feathers is not buff-brown but buff-grey or feathers may be "grey-based" and the pattern may be less well-defined.

The images on the right-hand side and table 5 present figures and illustrations of active wing-covert moult by July. In most birds, progress in wing-covert moult is most obvious in the lesser coverts, which show moult gaps in almost all individuals. Moult in the median and lower lesser coverts is finished in most birds, and by early July, many birds still show growing central greater coverts. The lesser coverts may show complete missing rows, exposing the bases of the fresh lower lesser coverts. In a few images, old second generation feathers are still in place: here and of course in this Swiss individual. The phenomenon of leaving older second generation coverts in place, while moult progresses in the same tract, was clear by June, but now by July, most of these old second generation are dropped as well, and may be an explanation for single grey and more adult-like feathers (see e.g. here and here). See Gull Topography for explanations of feather tracts.

As can be seen in many images of May, June and early-July 2cy michahellis, the sequence of moult in the wing-coverts is sometimes hard to obtain correctly. Post-juvenile feathers are maintained over a longer period and result in a 'jumpy' moult pattern and only after these old post-juvenile feathers are replaced for new third generation feathers, the wing-covert rows appear neat and tidy. It's the end of July then...

Moult stage and pace of scapulars:

Moult to third generation scapulars may start as early as mid-January in 2cy michahellis. By June, all present birds show active moult in the scapulars, with largest numbers for the class 75%-99% third generation scapulars (n = 24). By the end of July, this moult in the scapulars is completed, with fresh feathers in the lowest scapular row. 
Previous sections of 2cy michahellis show the most commonly seen moult sequence in the scapulars, starting with the lower upper scapulars and finishing with the rear lowest scapulars. So not surprisingly, its mainly the lowest scapulars which may still be in active moult by July, as is illustrated by this bird.

Tables:

Table 1 & 2: 2cy Larus michahellis July and 2cy Larus argentatus argenteus July primary scores to compare.

remaining old prims in Michahellis 03-06.07.01 10.07.02 10.07.02 27.07.01 27.07.01 28.07.01 30.07.01
Croatia(1) Etaples A Etaples B Etaples(2) A Etaples B Etaples Etaples
no - - - 12 15 23 21
P10 - 2 3 12 25 16 19
P9-P10 8 32 28 10 15 12 12
P8-P10 11 14 14 - - - -
P7-P10 8 - - - - - -
P6-P10 - - - - - - -
n: 27 48 45 34 55 51 52
average rem. P 3,0 2,3 2,2 0,9 1,0 0,8 0,8
95% CID(3)  0,31 0,15 0,17 0,28 0,20 0,23 0,22
Variance (s2) 0,62 0,28 0,33 0,66 0,56 0,65 0,62
SD (s) 0,78 0,53 0,57 0,81 0,75 0,81 0,79
SE (sx) 0,15 0,08 0,09 0,14 0,10 0,11 0,11
               
 
% old primaries:
0 - - - - - 45 40
1 - 4  7 4 7 31 37
2  30  67  62  67  62  24 23
3  41  30  31  29   31  - -
4  30 -   -   -    -   - -
% Control 101 101 100 100 100 100 100

Notes:
(1): Sample on Isle of Krk, Croatia by Peter Adriaens.
(2): Most samples are from Etaples, NW France. Here you find more about Etaples and Boulogne-sur-Mer.
(3): 95% Confidence Interval of the Difference.

 

 

remaining old prims in Argenteus 10.07.02 09.07.02 13.07.01 15.07.00 17.07.01 (15:00 h.) 17.07.01 (17:00 h.) 17.07.02 22.07.00
Boul Schev Schev Schev Schev Schev Schev Schev
0 1 - - - - - - 1
P10 4 - - 3 - 1 1 10
P9-P10 66 2 13 22 20 21 15 51
P8-P10 66 40 35 32 26 21 33 41
P7-P10 10 33 12 13 4 1 13 5
P6-P10 - 5 1 1 - 1 3 1
n: 147 80 61 71 50 45 65 109
average rem. P 2,5 3,5 3,0 2,8 2,7 2,6 3,0 2,4
95% CID(1) 0,11 0,15 0,18 0,20 0,18 0,21 0,21 0,15
Variance (s2) 0,48 0,43 0,48 0,69 0,39 0,48 0,69 0,63
SD (s) 0,70 0,66 0,70 0,83 0,62 0,69 0,83 0,79
SE (sx) 0,06 0,07 0,09 0,10 0,09 0,10 0,10 0,08
                 
% old primaries:              
0 1 -          -            -            -            -            -       1
1 3 -          -        4          -        2      2      9
2 45 3     21     31     40     47     23     47
3 45 50     57     45     52     47     51     38
4 7 41     20     18      8      2     20      5
5 - 6      2      1          -        2      5      1
% Control 101 100   100   99   100   100   101   101

Notes:
Boul: Boulogne, NW France.
Schev: Scheveningen: samples from beach and port, near The Hague, the Netherlands.
(1): 95% Confidence Interval of the Difference.

 

Cross-Tables Larus michahellis 2cy:

Table 3 - 8: 2cy Larus michahellis primary moult scores, horizontal new primaries, vertical old primaries in Etaples and Lignano, July.

table 3: 2cy michahellis primary scores: Etaples, NW France, July 10 2002, morning.
n = 45, m-new = 5.4, s-new = 0.53
n = 48, m-old = 8.8, s-old = 0.53
old / new p4 p5 p6 ? n:
p8 old - 10 1 3 14
p9 old 1 17 14 - 32
p10 old - - 2 - 2
n: 1 27 17 3 -

Notes: 

* ?: no full-grown primary visible.

 

table 4: 2cy michahellis primary scores: Etaples, NW France, July 10 2002, afternoon.
n = 42, m-new = 4.5, s-new = 0.51
n = 45, m-old = 8.8, s-old = 0.57
old / new p4 p5 p6 ? n:
p8 old 11 - - 3 14
p9 old 11 17 - - 28
p10 old - 3 - - 3
n: 22 20 - 3  

Notes: 

* ?: no full-grown primary visible.

 

table 5: 2cy michahellis scores: Lignano, Venice July 27 and 29th 2001.
prim* score

n: 137
30: 31: 32: 33: 34: 35: 36: 37: 38: 39: 40:
3 2 3 1 4 4 4 10 4 8 6
  41: 42: 43: 44: 45: 46: 47: 48: 49: 50:  
  8 13 24 20 12 3 3 1 2 2
fully grown: p5 p6 p7 p8 p9 p10   n: 137
8 18 44 56 9 2
tail moult none: 1-2 pairs 3-4 pairs 5 pairs all new n: 63
4 4 15 21 19
moult in lesser coverts: none some - -
25 3 - n:28
moult in median coverts: few: 50% 100% -
3 14 11 n: 28
moult in greater coverts: none inner in+outer -
10 12 6 n: 28

*: prim score = primary moult score, see Topography for explanation. Old feathers score 0, fully grown feathers score 5, so prim score runs from 0 to 50.

 

table 6: 2cy michahellis primary scores: Etaples, NW France, July 27 2001.
n = 55, m-old = 10.0, s-old = 0.75
n = 55, m-new = 6.4, s-new = 0.50
old / new p5 p5+ p6 p6+ p7 ? n:
p9 old - 1 14 - - - 15
p10 old - - 17 - 7 1 25
0/p10 old - - - - 1 - 1
0 old - - - 1 13 - 14
n: - 1 31 1 21 1 -

Notes: 

* 0 old: no old primaries in the outer wing. 
* 0/p10 old: still one old primary in one wing, the other p10 shed.

* p5+: p6 already longer than p5, but not yet full-grown.

* ?: no full-grown primary visible.

 

table 7: 2cy michahellis primary scores: Etaples, NW France, July 28 2001.
n = 51, m-new = 6.4, s-new = 0.45
old / new p6 p6+ p7 n:
p9 old 12 - - 12
p10 old 11 4 1 16
0/p10 old - 4 1 5
0 old 1 2 15 18
n: 24 10 17 -

Notes: 

* 0 old: no old primaries in the outer wing. 
* 0/p10 old: still one old primary in one wing, the other p10 shed.

* p5+: p6 already longer than p5, but not yet full-grown.

* ?: no full-grown primary is visible.

 

table 8: 2cy michahellis primary scores: Etaples, NW France, July 27 2001.
n = 51, m-new = 6.6, s-new = 0.51
old / new p5+ p6 p6+ p7 p7+ p8 n:
p9 old - 10 1 - - - 11
p10 old 1 3 10 5 - - 19
0/p10 old - - 1 1 - - 2
0 old - 2 - 15 1 1 19
n: 1 15 12 21 1 1 -

Notes: 

* 0 old: no old primaries in the outer wing. 
* 0/p10 old: still one old primary in one wing, the other p10 shed.

* p5+: p6 already longer than p5, but not yet full-grown.

 

 

5693.jpg (111654 bytes)photo 5693: 074S michahellis 2cy, July 28 2001, Etaples (France). Ringed white right 074S and born in the Camarque, year 2000. 
5621.jpg (105832 bytes)photo 5621: 255S michahellis 2cy, July 27 2001, Etaples (France). Ringed white right 255S, born in the Camarque, year 2000.
5692.jpg (105779 bytes)photo 5692: 114T michahellis 2cy, July 28 2001, Etaples (France). Ringed white right 114T, born in the Camarque (S. France) in year 2000.
2cy michahellis in July, ringed in Switserland. (101700 bytes)Sempach 885629 michahellis 2cy, July 10 2002, Boulogne/Mer, France. A ringed michahellis from Switzerland. Delayed moult compared to 2cy michahellis from S France.
2cy michahellis in July, ringed in Spain. (101926 bytes)NTT8 michahellis 2cy, July 11 2003, Amsterdam, the Netherlands (52.21N 04.52E). Bird seen in 1cy, 2cy and 3cy in Amsterdam.

 

5567.jpg (107046 bytes)photo 5567: michahellis 2cy, July 27 2001, Le Portel (France). P7 almost fully grown. P10 still juvenile.
5715.jpg (96773 bytes)photo 5715: michahellis 2cy, July 30 2001, Le Portel (France). P10 still juvenile and p7 already longer than p6 but still not full-grown. Legs pink-yellow, bill black.
5548.jpg (82076 bytes)photo 5548: michahellis 2cy, July 26 2001, Le Portel (France). A huge individual, probably a male, resembling L. marinus.
5550.jpg (103697 bytes)photo 5550: michahellis 2cy, July 26 2001, Le Portel (France). Beneath the tertials, p4, 5 and 6 are visible and full-grown; p9-p10 are still juvenile. 
5704.jpg (99492 bytes)photo 5704: michahellis 2cy, July 30 2001, Le Portel (France). P7 is full-grown and there are no old juvenile primaries left. Moult is going on in the scapulars and lesser coverts.
5573.jpg (92018 bytes)photo 5573: michahellis 2cy, July 27 2001, Le Portel (France). No old primaries. Moulting lesser coverts and scapulars. 
5619.jpg (36020 bytes)photo 5619: michahellis 2cy, July 28 2001, Le Portel (France). Showing secondary moult strategy end of July.
5688.jpg (103781 bytes)photo 5688: michahellis 2cy, July 28 2001, Le Portel (France). P10 is still old, p6 is full-grown.
5540.jpg (112023 bytes)photo 5540: michahellis 2cy, July 26 2001, Le Portel (France). P7 full-grown and p8 at the length of p5. Moulting the scapulars to adult-like grey feathers.
5570.jpg (101969 bytes)photo 5570: michahellis 2cy, July 27 2001, Le Portel (France). P10 still juvenile, p7 full-grown. Fresh 2nd generation-like tertials. 
5577.jpg (89220 bytes)photo 5577: michahellis 2cy, July 27 2001, Le Portel (France). All juvenile primaries shed, p7 almost full-grown, p8 at the length of p4. Note the red orbital ring in 2cy.
5713.jpg (103990 bytes)photo 5713: michahellis 2cy, July 30 2001, Le Portel (France). Pale, colourless legs and black bill. Head moulted to 2nd winter. The tail feathers are simultaneously growing.
1838mich2cy.jpg (74202 bytes) er zijn nog vele begin juli micha's in de map.
5627.jpg (99805 bytes)photo 5627: michahellis 2cy, July 27 2001, Le Portel (France). Probably the most advanced moult stage found in 2cy michahellis by the end of July.
5437.jpg (77196 bytes)photo 5437: argentues 2cy, July 14 2001, IJmuiden, the Netherlands.  
Herring Gull in 2cy to compare.
5562.jpg (94504 bytes)photo 5562: argenteus 2cy, July 27 2001, Le Portel (France).