September 2003 - September 2004, IJmuiden, the Netherlands (52.27N-04.33E).
A 2cy argenteus
with a Dutch ring: Vogeltrekstation Arnhem 5.412.501; ringed as
"fledged 1cy" on September 09 2003 at IJmuiden (52.28N 04.35E).
It was held in captivity for more than 24 hours. The ringer aged this bird
1cy, an easy mistake considering the pattern on the wing-coverts, which is
still very first generation like.
From late April onwards, argenteus has a complete moult
during summer to so-called "second winter" plumage. This
complete moult will be finished by October. The head has been moulted in July-August and shows neat fine
streaking by October. The under-parts and rump are pale, mottled with
brown. From mid-May, the scapulars and mantle were replaced for third
generation feathers, starting with the replacement of the lower upper
scapulars. The pattern of the third
generation scapulars is more or less similar to the anchor pattern of the
second generation feathers. In argenteus,
some new scapulars may appear adult-like pale grey, but most new
feathers will show an anchor pattern and this still applies on the new
feathers in September. By September, 2cy argenteus is actively
moulting the lowest scapulars, but in the mean time, the upper scapulars
may be moulted again as well. Fresh feathers can be recognized by the
From early April, the inner primaries
and new second generation primaries grown in. On average, the last juvenile primary (P10)
was shed in the first week of August. The majority of argenteus
complete the primary moult by the first week of October, when the new second
generation P10 will be fully grown. The new primaries are dark with a tiny pale tip on
the fresh flight-feathers. The four inner primaries show an extensive
pale window, as both inner and outer-web are pale greyish white-brown,
contrasting with the outer-wing. A pale inner-web can still be found in P7.
The second generation
tail-feathers show a clear-cut blackish tail-band with only isolated
blackish markings on the white basal half.
From late April to September, argenteus replace the wing-coverts and
tertials, finishing with the central greater coverts and outer lesser
coverts. By September, the average 2cy argenteus start a
simultaneous partial autumn moult in the wing-coverts, including the upper
tertials, some median and lower lesser coverts and often the inner greater
Arnhem 5.412.501 has primary
P9 fully grown. The partial wing-covert moult didn't start yet, since the inner
greater and inner median coverts are still present. In general, this is
still a very 'barred 2cy individual'.
top image: Herring
September 22 2003, IJmuiden.
2 images below: Herring
November 11 2003, IJmuiden.
The complete moult in argenteus is
finished by late-October and overlaps with the partial autumn moult which
starts in September and often include scapulars, a few inner wing-coverts
and upper tertials. The head shows neat fine streaking and the under-parts
and rump are pale, mottled with brown. The scapulars and mantle are
replaced for third generation feathers, finishing with the replacement of
the rear lowest scapulars. The pattern of these third generation scapulars
is more or less similar to the anchor pattern of the second generation
feathers. Simultaneous with replacement of the lowest scapulars, argenteus
moult some of the lower upper scapulars in November. By October, argenteus
the new scapulars may appear adult-like pale grey or grey-based.
By late-October to November, argenteus
has finished the primary moult. The second generation tail-feathers show a
clear-cut blackish tail-band with only isolated blackish markings on the
white basal half.
image below: Herring
March 20 2004, IJmuiden.
2 images below: Herring
May 11 2004, IJmuiden.
2 image below: Herring
July 09 2004, IJmuiden.
1 image below: Herring
September 18 2004, IJmuiden.
From June to October, a complete moult
will bring 3cy argenteus in so-called "third winter"
plumage. By September, when the complete moult is (almost) finished, the
head will show extensive 'winter streaking', mottled brown contrasting
with the white breast as in an executioner's hood. The scapulars and
mantle are pale adult-like grey, although some individuals may show an
immature pale brown hue on the lower scapulars.
By the end of the complete moult (October), all wing-coverts have been
replaced, most to plain grey feathers. Immature patterns can often be
found in the lower tertials, greater coverts and outer lesser coverts (the
During the 3cy summer, the primaries are moulted to third generation. The
first inner primaries are dropped by late May and the outer primary P10
will be dropped by late August. The primary moult is completed by
late-October in argenteus, when the new outer primary P10 is fully
grown. The table below shows some September data from Scheveningen harbour.
The third generation primaries are clearly adult-like, with the inner
primaries P1-P4 plain grey with a white tip. The outer-wing shows a clear
black triangle, extending on the greater primary coverts. From P4
outwards, the primaries show a black sub-terminal band. The white primary
tips are obvious in the inner primaries, but only poor developed on P9 and
P10. P10 has a small white mirror (lacking in some birds). The new
tail-feathers will be white, with clear immature black markings. The iris
turns pale yellow in summer (from July onwards).
primary moult scores in 3cy Herring Gulls at Scheveningen.
By September, local argenteus get company from argentatus
from Norway, which have on average lower moult scores and from argentatus
from the Baltic region, which have equal moult scores probably.
95% CID: Confidence Interval of the Difference.