Herring Gull - Zilvermeeuw (argentatus & argenteus)

(last update: 08 december 2003)

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Herring Gull V173adult (argentatus), November 17 2002, Westkapelle, the Netherlands (51.33N-03.25E).

This individual is ringed in Denmark: yellow V173 (but faded white) and metal ring Copenhagen 37173. P9 is fully grown and P10 is already as long as P8, PMS: 49. The orbital ring is orange-red, slightly darker than what is commonly found in western argenteus. The sub-terminal black markings on P10 are lacking and the medial band on P10 only covers a limited range of the edge of the inner-web. The inner wing-coverts and upper tertials still have fresh fringes, in much better condition than found in some argenteus, which have these feathers replaced about 4 months ago and show worn fringes by November. The bill in this bird is slightly paler at the base. 

From June (often mid-May in France, Belgium and the Netherlands) to October, a complete moult will bring birds in so-called "adult winter" plumage. A new set of primaries will grow during the summer months and by late November, the average argenteus in the Netherlands and northern France has completely moulted all primaries. At the same time, the wing-covert moult is completed by the end of the month. 
In summer, the head is still largely white, but by September, most adults develop extensive 'winter streaking', in sub-adults strongly mottled brown contrasting with the white breast as in an executioner's hood. The scapular coverts are plain grey, lacking white crescents. The tertials show obvious white tips. The iris is yellow. The bill is yellow with a red gonydeal spot confined to the lower mandible. The orbital ring is yellow-orange in most argenteus