Herring
Gull - Zilvermeeuw (argentatus & argenteus): sub-adult January
(last update: 08 december 2003)
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(2 images) Herring Gull sub-adult (argentatus), January 03 2002, Le Portel / Boulogne-sur-Mer, France (50.42N,1.34E).
As a resting bird with
folded wings, this individual may easily be taken for 3cy, with the
complete brown P10 lacking a mirror, the rather dull-brown immature outer
primaries, the densely barred greater coverts and many of the lesser
coverts. However something seems to be wrong...
Then the bird stretches the wings, revealing the third generation inner
primaries and suddenly the obvious white tail-feathers can be understood,
which already seemed odd lacking a broad tail-band. The advanced bill
coloration falls in place as well: it proves to be a 4cy bird!
But its a nice example of a bird showing obvious immature features, especially on the greater and lesser coverts, lower tertials, tail-feathers and bare part coloration. Some Scandinavian argentatus moult in a very slow pace, illustrated in this 4cy bird.
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.
