Coordinators:
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Gabriel Martín
Antonio Gutierrez
Amir Ben Dov
Mars Muusse
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Larus michahellis - 3CY July 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
Early July and from
July 26-30 2001 we did small surveys on Yellow-legged Gulls at Le
Portel (near Boulogne-sur-Mer) and Etaples (near Le Tourquet). In these surveys, we
scored moult stages to determine timing of moult in primaries (and wing-
coverts and body-feathers) in 3CY michahellis.
The general appearance of 3CY michahellis is rather
straightforward. Most birds can still be recognized by the plain grey
upper-parts, combined with barred wing-coverts. The bare parts are
typically a red orbital
ring and yellow legs. An example of the average michahellis can be found in the first image, an individual ringed near Marseille, S France, showing active
moult in the wing-coverts and only the outer two primaries are still old
second generation.
For
details on differences between michahellis and cachinnans, see
e.g. the article by R. Klein & D. Gruber in Limicola, April
1997.
Moult
stage and pace of remiges and rectrices
The complete moult started by mid-May,
when 3CY birds dropped the innermost primary P1. By early July, the
average score has strongly increased: P7-P10 are still old secnd
generation and all inner primaries are missing or new. Since the
tips of P5 and P6 normally extend beyond the tertials (especially
the abraded July tertials), the moult gap of missing P5 and P6 is
obvious.
3CY michahellis continue shedding primaries throughout the
month, and by the end of July, the average primary moult score is
8.5, hence 50% have only P9 and P10 old, the other 50% has P8-P10
old. With this score, 3CY birds are about two primaries behind compared to 2CY birds (which have a score of 9.2: 45%of 2CY have shed all primaries by
late July).
As in adults, the gap between full-grown primaries and remaining old
primaries is in general about three feathers,
but often slightly more as the table shows. This large moult gap is
typical for michahellis, and not found in e.g. Dutch argenteus.
By the time P4 is fully grown, 2CY
birds normally start the complete moult in secondaries and rectrices.
The ordinary moult strategy in 3CY birds may be slightly later
(starting when P5 is fully grown. Note however that individual
variation may exist, particularly in 3CY michahellis rectrices moult as this moult may follow an irregular pattern in
earlier months. The
partial spring moult has finished in June and a small minority of 3CY
June michahellis have included some rectrices in this partial moult. Hence, it's not uncommon
to find 3CY birds showing plain white tail-feathers, in some birds
creating a 'blocked' tail pattern already, prior to the complete
moult. On average, the common sequence is centrifugal moult:
starting with the inner tail-feathers and continuing symmetrically
outwards to both outer feathers.
Secondary moult hasn't started yet in late-July, but
is initiated in early-August. The images on this page showing
birds with open wings illustrate that all outer secondaries are
still present. By early August, the outermost secondaries (S1 &
S2, at the division between secondaries and primaries) are normally
dropped individually, but the central secondaries are shed almost as
in small groups, creating large gaps of missing secondaries, nicely
illustrated by this flying 2CY
bird and this stretching 3CY
August michahellis.
Timing and
strategy of body & covert moult in July
Wing-covert moult in 3CY and sub-adult michahellis vary
between individuals. See e.g. 365D,
showing extensive moult in the wing-coverts (the sequence is mentioned in the accompanying
text). Such birds contrast strongly with e.g. this
bird, which has almost all the wing-coverts old.
In general, conclusions based on average 3CY michahellis are:
- Moult of head feathers is in
progress, creating a streaked head in the advanced individuals.
See here (streaking) and here ("moth-eaten" head in 365D).
- 3CY birds show plain adult-like
grey scapulars. It's
difficult to score missing feathers in the complete grey
upper-parts, hence we have no scapular moult scores. In general,
the scapulars in the lowest row look very fresh, without
abrasion at the fringes and lacking the faded grey tone, so
scapular moult may be near its end in 3CY michahellis by
the end of July.
In some
individuals, the scapular region contains some old and abraded feathers
(in the upper region of the upper scapulars),
sometimes showing a brown hue, others are bleached white-grey
with only a slightly darker shaft-streak. However, most birds have the
entire back adult-like grey.
- The complete wing-covert moult is in progress throughout July. The
ordinary moult strategy and sequence start in the outer median
coverts, the innermost medians and innermost greater coverts, the upper tertial
and the outer lower lesser coverts. Early July, the new median
coverts are visible (first the outer median coverts), more so as
the outer lower lesser coverts are dropped. By the end of July,
the complete median covert bar is renewed, the lower lesser
coverts are growing, the outer greater coverts are missing
(exposing the secondaries underneath) and the innermost greater
coverts have been renewed. In the tertials, the new upper two
feathers are visible and the central tertials are dropped.
See Topography
Section for explanation of feather tracts.
Tables
The surveys
were done at resting and preening 3CY sub-adults (with at least
no white mirror at P10 and at least some obvious second summer feathers).
3CY michahellis primary scores: Etaples, NW France, July 2001
& 2002. |
old
primaries |
July
10 2002 |
July
29 2001 |
July
30 2001 |
p6
old |
6 |
- |
- |
p7
old |
21 |
- |
2 |
p8
old |
6 |
19 |
25 |
p9
old |
- |
20 |
24 |
p10
old |
- |
- |
1 |
no
old |
- |
- |
1 |
n: |
33 |
39 |
53 |
m: |
7.0 |
8.5 |
8.5 |
s: |
0.61 |
0.51 |
0.70 |
. |
notes:
3CY birds selected on bare part coloration, tail pattern, pattern on
innermost secondaries and outer greater primary coverts. |
3CY michahellis scores: Lignano, Venice July 27 - 29 2001. |
prim*
score
n: 41 |
30: |
31: |
32: |
33: |
34: |
35: |
36: |
1 |
0 |
1 |
4 |
2 |
3 |
7 |
37: |
38: |
39: |
40: |
41: |
42: |
43: |
4 |
8 |
3 |
3 |
2 |
2 |
1 |
fully**
grown: |
p5 |
p6 |
p7 |
p8 |
n: 42 |
1 |
12 |
25 |
4 |
tail
moult |
none: |
in
progress: |
complete
new: |
n: 18 |
1 |
6 |
11 |
*: 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.
**: 1 bird did not miss a single primary. |
oldest
primaries \ full-grown primaries
in 3CY michahellis, Etaples, July 29-30 2001.
n = 92, m = 8.5, s
= 0.58 |
. |
p4 |
p4+ |
p5 |
p5+ |
p6 |
p6+ |
? |
n =
92 |
% |
p=0 |
- |
- |
- |
- |
- |
1 |
- |
1 |
1% |
p10 |
- |
- |
- |
- |
1 |
- |
- |
1 |
1% |
p9 |
- |
3 |
16 |
15 |
7 |
1 |
2 |
44 |
48% |
p8 |
8 |
12 |
9 |
- |
- |
- |
15 |
44 |
48% |
p7 |
- |
- |
1 |
- |
- |
- |
1 |
2 |
2% |
Notes:
Aggregated scores of two dates. Average on both dates 2.49 remaining
primaries.
*
Oldest primary: the first primary to be shed
next.
*
P=0: no old primaries in the outer wing (1 individual); p7
means p7-p10 are still old and p7 will be the next primary to be shed (2
individuals).
*
p4 as full-grown primary: p1-p4 are new. P4+ means p4 is the last
full-grown primary but already, p5 is longer than p4 but just not yet
full-grown, thus p4 last full-grown primary.
*
?: no full-grown primary is visible (e.g. in resting individuals). In most cases this can be read as 'p5 yet not
full-grown', because in most cases p5 would be visible in a resting bird
because this primary is slightly longer than the longest (primaries
covering) tertial. |
|
Yellow-legged
Gull michahellis 3CY 365D July 27 2001, Etaples,
France. From Camarque, S France 1999. P5 is almost full grown, p9-p10
are old. |