Herring Gull - Zilvermeeuw (argentatus & argenteus): sub-adult March
(last update: 08 december 2003)
Herring Gull 4cy (argenteus), March 17 2003, Boulogne-sur-Mer, France (50.42N,1.34E).
This is clearly a sub-adult with the scapulars completely adult-like grey
while the wing-coverts and the tertials show some barred feathers. Note
also the brown hue on the greater primary coverts, the greenish hue on the
iris and the extensive black on the bill.
From January to April, 4cy argenteus 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.