Herring Gull- Zilvermeeuw (argentatus & argenteus)

(last update: 5-11-2006)


Herring Gull plumages:

hg 1cy July
hg 1cy August
hg 1cy September
hg 1cy October
hg 1cy November
hg 1cy December

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

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

hg sub-ad January
hg sub-ad February
hg sub-ad March
hg sub-ad April
hg sub-ad May
hg sub-ad June
hg sub-ad July
hg sub-ad August
hg sub-ad September
hg sub-ad October
hg sub-ad November
hg sub-ad December

hg ad January
hg ad February
hg ad March
hg ad April
hg ad May
hg ad June
hg ad July
hg ad August
hg ad September
hg ad October
hg ad November
hg ad December

Herring Gull C9C37 1-2cy (argentatus), August 2002 & July 2003, Tampere, Finland (61.31N,23.43E).

below: C9C37 1cy (argentatus), August 08 2002, Tampere, Finland (61.31N,23.43E).

A 1cy argentatus, ringed in Finland: white C9C37, seen on August 08 until August 11 2002. This individual is in complete juvenile plumage and shows hardly any wear on the upper-parts. Argentatus in juvenile plumage has the head and under-parts streaked grey-brown, rather pale on forehead and throat and with dark ear-coverts. The mantle and scapulars are brown based with buffish-yellowish fringes when the feathers are fresh, with shiny white fringes when the feathers are older. The notched pattern is repeated on the lesser, lower lesser and median coverts, although the medians have paler centres. The greater coverts show a 'piano-key' pattern; also on the outer greater coverts in argenteus, but sometimes these outer greater coverts have extensive dark centres and a thin fringe in argentatus
The tertials have an obvious notched pale fringe and transversal bar, although some argentatus have a pattern much similar to michahellis, with only a very narrow straight white fringe and an extensive dark brown centre. 
The secondaries, primaries and primary coverts are dark with a small white tip (obvious on some birds), but the inner primaries show a pale window, prominent from below and above. The under-wing is rather uniform grey-brown patterned. The tail has a broad sub-terminal band and isolated dark bars on the basal half. Some argentatus have a broken tail-band similar to 1cy marinus, with deep notching. The iris is dark, the bill is blackish, sometimes with a paler base, and the legs are flesh-pink. 

The partial autumn moult (moult into so-called "first winter" plumage) includes the body and head feathers. This moult may start as soon as the nest is abandoned. Due to the wide breeding range of argentatus in Scandinavia, from Denmark to the far north of Norway and Russia, much variation exists regarding the commencement of this partial moult. We did a small survey in Tampere, SW Finland in the second week of August. The results are presented in the table below. Over 50% of the 1cy argentatus started scapular moult and about 1/3 of the birds showed second generation scapulars. However, with severe winter conditions in northern Scandinavia, 2cy argentatus may turn up along the coast of the Netherlands, still in complete juvenile plumage by January. These birds are believed to origin from the far northern Scandinavian and Russian populations.
In the partial moult, the upper breast and head turns paler on throat and forehead. The feathers on belly and vent will still be juvenile in most 1cy argentatus by November. From August onwards, the mantle and upper scapulars are moulted to second generation feathers, showing an anchor pattern and a dark base. The lowest row of scapulars will be still juvenile by April in most 2cy birds (contra e.g. michahellis). The juvenile wing-coverts, rectrices and remiges start to bleach and show wear in the fringes from September onwards in the southern populations.

In the table below, the scapular moult scores of 1cy August argentatus in Finland can be read:

1cy argentatus in August, Tampere landfill, Finland, August 10 2002, 10:00-12:00 h.
  total :
all scaps juvenile 50 (41%) incl orange C211J
some scaps missing 35 (29%)
1-5 scaps new 13 (11%)
6-10 scaps new 13 (11%)
11+ scaps new 10 (8%)
total sample size, n: 121.

 3 images below: C9C37 2cy (argentatus), July 15 2003, Tampere, Finland (61.31N, 23.43E).

A 2cy argentatus, ringed white C9C37 as pullus on June 24 2002 in Vkoski, Finland (61.17N 24.09E). The complete moult is well underway with most wing-coverts and the inner primaries moulted to second generation. Primary P8 has been dropped and P9-P10 still juvenile. P1-P6 are fully grown second generation flight-feathers. All tail-feathers, except one (R5 or R6) are dropped and growing second generation.
Most tertials and the wing-coverts are replaced for second generation feathers. The central greater coverts are still growing: the gap in the greater covert row is almost closed. Last juvenile wing-coverts can be found in the lesser coverts.

By July, the warm brown tones of the first moulted second generation feathers (inner greater coverts and inner median coverts) are faded to plain white, leaving a contrasting barred pattern on the wing-coverts. On average, 2cy argentatus is more contrastingly patterned than same aged 2cy argenteus, especially regarding the pattern on the central greater coverts. However, some argentatus are distinct "washed out" brown, showing the common vermiculated pattern of 2cy argenteus
The last moulted coverts are the central greater coverts and outer lesser coverts, replaced by mid-August. From mid-August onwards, 2cy argentatus start the partial autumn moult, starting again to drop the upper tertial and inner greater and median coverts. 

In the tables below, the primary moult scores of 2cy July argentatus in Finland can be read:

Primary moult score of 2cy argentatus Herring Gull, at Tampere landfill, Finland (61.33N, 23.59E) on July 10 2003.
. P4 fg P5 fg P6 fg P7 fg ? fg n:
P6-P10 - - - - - -
P7-P10 5 4 - - 6 15
P8-P10 1 54 6 - 13 74
P9-P10 - 11 34 - 2 47
P10 old - - 1 1 - 2
n: 6 69 41 1 21 138
n = 138; m old P = 2.7; SD old P = 0.67.
Survey at Tampere, landfill, in resting group at 'the saddle', about 200 2cy Herring Gulls, probably 100% argentatus.
P6-P10 = P6-P10 are still old and present.
? fg = fully grown not known. Fully grown primary score most probably P6 or less.
fg = fully grown. In our field surveys, a primary is 'fully grown' when it exceeds the previous feather in the folded wing. Actually,  such 'fully grown' feathers may have to grow a little, but under field circumstances, it's very difficult to find out if the waxy sheath, which is the standard measurement for fully grown primaries, is still present. 


Primary moult score of 2cy argentatus Herring Gull, at Tampere landfill, Finland (61.33N, 23.59E) on July 13 2003, 15:00 h.
. P4 fg P5 fg P6 fg P7 fg ? fg n:
P6-P10 - - - - 1 1
P7-P10 2 - - - 4 6
P8-P10 - 26 6 - 18 50
P9-P10 - 20 52 1 5 78
P10 old - - 5 3 - 8
n: 2 46 63 4 28 143
n = 143; m old P = 2.4; SD old P = 0.69.
Survey at Tampere, landfill, in resting group at 'Bio I'.