Introduction

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 powerful birds in the northern populations, showing the most darkest upper-parts, longest wing and most white in the outer-wing. 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 paler mantled argentatus often show a limited black sub-terminal spot on P5 in adult plumage.
On these 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".

2cy Herring Gull April: tables and charts

April-Chart 1 (below): 2cy HG primary scores in 2002, except May 11 & 26 from 2001 (n = 903). Data as in table 2. Chart 1 shows the early primary moult stage for 2cy Herring Gull; the complete spring - summer figure is plotted in chart 2.

April-Chart 2 (below): 2cy HG primary scores in 2002 and 2001 (n = 2.632). Cumulative data plot for primary moult in spring - summer. Plot: remaining old primaries (e.g. 10 = P1-P10 old; 5 = P6-P10 old). Most data from Scheveningen harbour, Netherlands, but also Dannes and Le Portel, NW France. NW France data responsible for some peak values, e.g. July 10 and in late July indicating advanced primary moult stage compared to birds from Scheveningen. One may discuss including such data in this plot.