Herring Gull - Zilvermeeuw (argentatus & argenteus): sub-adult January
(last update: 08 december 2003)
Herring Gull sub-adult (argentatus), January 05 2002, Le Portel / Boulogne-sur-Mer, France (50.42N,1.34E).
In many respects this
bird shows immature features, especially on wing-coverts, tertials, tail
and bare part coloration. However, note the white tips on
the primaries and the large mirror on the fourth generation outer primary P10. This
combination of adult-like primary pattern and the immature outer rectrices still showing
black markings and the rather smudgy brown-green coloured iris, indicate it
is most probably a 4cy bird. But remember that some Scandinavian argentatus moult in a very slow
pace and this bird might already be in its fifth calendar year.
From January to April, 4cy argentatus moult to so-called "third summer" plumage. By April, the head and under-parts will appear all-white. The tail-feathers, wing-coverts and primaries are not replaced, therefore most birds strongly resemble "third winter" birds, although the white primary tips wear away and dark patches start to bleach. The iris is often yellowish, the orbital ring yellowish-orange and the bill predominantly yellow with a red gonydeal spot and limited black markings along the culmen by April.