Herring Gull- Zilvermeeuw (argentatus & argenteus)
(last update: December 15, 2011
Herring Gull 1cy (argentatus), August 14 2002, Götenborg, Sweden.
A very pale 1cy argentatus, with extensive white in the tips of the outer primaries. It recalls some birds labeled as hybrid hyperboreus x argentatus. This bird still frequented the nest site in SW Sweden, and is probably just on the very pale end of nominate argentatus, at least highly unlikely to be a hybrid. The tail has very much white as well, recalling marinus.
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 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 table below, the scapular moult scores of 1cy August argentatus in Finland can be read: