Herring Gull- Zilvermeeuw (argentatus & argenteus)

(last update: 3-1-2007)


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

(2 images) Herring Gull 2cy (argentatus), July 14 2003, Tampere, Finland (61.31N, 23.43E).

A 2cy argentatus. In many respects an average moult score for mid-July at Tampere. The complete moult is halfway with most wing-coverts and the inner primaries moulted to second generation. Primary P10 is still juvenile. P1-P6 are fully grown second generation flight-feathers; P7 is just shorter than P6. Note the narrow dark shaft-streaks and arrow-heads at P1-P3.
All median and greater coverts have been replaced, but a few juvenile wing-coverts are just visible in the upper row of lesser coverts. The fresh second generation coverts look very second generation like, being strongly barred. 
The open wing in the bottom image nicely illustrates the moult sequence of secondaries: the first replaced secondaries (S1) grow in at the division with the primaries, but soon the complete central secondary tract is dropped and will grow in simultaneously. Another moult wave is initiated at the tertials (which can be classified as secondaries as well) and the two waves meet at about secondaries #17.  

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'.