Herring Gull (argentatus & argenteus)

(last update: February 11, 2013)

Herring Gull sub-adult, April 17 2014, Katwijk, the Netherlands.

Maybe 3CY, with 2nd generation flight feathers, but could well be slightly retarded 4CY.
In most birds, a view on the inner primaries in flying birds will clinge age in sub-adults: 3CY birds have brownish inner primaries and the sub-terminal pattern in the central primaries is less developed, often brownish as well, not deep blackish as in 4CY birds. This age characteristic is then supported by the secondary pattern (extensive brown in 3CY birds, basically greysih in 4CY birds); tail pattern (normally broad band in 3CY birds); and extent of grey on the back.

The bird below is intermediate in these features, making ageing less obvious, even in this open-wing picture. There is brown on the inner primaries and the pattern on the central primaries is diffuse, brownish. However, the pattern on the secondaries better match 4CY birds, and so is the pattern on the tail. The outer primaries, brownish and lacking a mirror on P10, are of no help here in ageing this bird.