Herring Gull - L. argentatus

This website deals with the Herring Gulls of the taxa argentatus and argenteus. Argenteus is an abundant breeding species on Iceland, Britain, NW France, Belgium, the Netherlands and N Germany. The taxon argentatus breeds in NE Europe, from Denmark, the coast of the Baltic Sea, Scandinavia and coast of the White Sea. In the centre of the breeding range (Denmark and the NW German coast), birds show intermediate characteristics, indicating there is a cline in argenteus-argentatus. Argenteus in Western Europe is pale-backed, slightly smaller and with relatively much black in the wing-tip; argentatus in the NE Europe is larger, slightly darker on upper-parts and show less black in the wing-tip.
Due to the large breeding range, there is much intra-specific variation in argentatus, with most large, powerful birds in the northern populations, showing the most darkest upper-parts, longest wing and most white in the outer-wing. In this region, some populations may hold substantial number of yellow-legged argentatus. (referred to as "Finnmark yellow-legged argentatus"). In adult plumage, the black sub-terminal spot on P5 is often lacking or strongly reduced to a diffuse streak, broken at the centre. Sometimes P6 lacks black as well.
In the Baltic region, other yellow-legged argentatus populations occur ("Baltic yellow-legged argentatus"), with adults showing even brighter yellow legs in summer and the upper-parts only slightly darker than West European argenteus, still much paler than Yellow-legged Gull (michahellis). Those Baltic argentatus often show a black sub-terminal spot on P5 in adult plumage.
On these web-pages, we largely follow P.J. Grant: "Gulls, a guide to identification" and E.K Barth's publication as Contribution No. 86, Zoological Museum, University of Oslo: "The circumpolar systematics of Larus argentatus and Larus fuscus with special reference to the Norwegian populations".

remaining SPRING
starting date:	30 Apr	07 May	14 May	21 May	04 Jun	11 Jun	30 Jul
week no:	18	19	20	21	23	24	31
0	0	0	0	0			0
1	0	0	0	0			0
2	0	0	0	0			1
3	0	0	0	0			1
4	0	0	0	0			37
5	0	0	0	0			22
6	0	0	0	0			3
7	3	2	1	2			0
8	16	22	26	18	1	1	0
9	30	13	16	10	1		0
10	66	33	37	10			0

n=	115	70	80	40	2	1	64
average REM P:	9.4	9.1	9.1	8.7	8.5	8.0	4.4
95% CID =	0.15	0.23	0.20	0.29	6.35		0.17
inverse =	1.98	1.99	1.99	2.02	12.71		2.00
Variantie (s²) =	0.68	0.90	0.84	0.83	0.50		0.46
SD (s) =	0.82	0.95	0.91	0.91	0.71		0.68
SE (s_x) =	0.08	0.11	0.10	0.14	0.50		0.09

% class:
0	0	0	0	0	0	0	0
1	0	0	0	0	0	0	0
2	0	0	0	0	0	0	2
3	0	0	0	0	0	0	2
4	0	0	0	0	0	0	58
5	0	0	0	0	0	0	34
6	0	0	0	0	0	0	5
7	3	3	1	5	0	0	0
8	14	31	33	45	50	100	0
9	26	19	20	25	50	0	0
10	57	47	46	25	0	0	0

% control:	100	100	100	100	100	100	100

Table above, data for the Netherlands (2000-2010), results for spring & summer (aggregated week): number of remaining old primaries in adults.
0 = 0 old primaries left (P10 dropped); 10 = all 10 primaries still old and present.

Above: Scatter Plot for PMS in adult Herring Gulls. Number of remaining old primaries throughout the year. Sample size is 1.329 birds.

Above: Scatter Plot for PMS in adult Herring Gulls throughout the year. Longest new primary is classified "fully grown". Sample size is 3.271 birds. Birds scored on NEW primaries.

Onset of primary moult can best be illustrated by a sinusoid for the first few weeks and last weeks, but there appears to be linear dependency over much of the central moult period.