(4 images) sub-adult intermedius LBBG, October 19 2002, Brouwersdam, the Netherlands.
A bird which is arresting the moult at P7. P1-P6 have been replaced and P7 is clearly longer than P6, while P8-P10 are still present. The old P10 has a clear mirror but on P9 the mirror is lacking. It's a rather long-winged bird with P6 leveling with the tail-tip and P10 clearly longer than P9, not seen in many intermedius LBBG. Note the large primary steps between the tips of the primaries.
All rectrices are all-white.
In both wings, all wing-coverts are present. The fresh wing-coverts are pitch-black (see the 1st and 2nd picture, taken in full sun and taken with clouded sky. A few coverts still have a strong brown hue.
The yellow bill has an black line along the culmen and a red gonydeal spot. The legs are yellow. The orbital ring is red and the yellow iris is only sparsely peppered black.
The winter streaking on the head create a hooded effect.
The general appearance advocates intermedius: a short thick neck, short legs, attenuated rear end, dove-like body, and the advanced primary moult stage compared to fuscus.
image 1: in full sun.
image 2: with clouded sky.
image 3: with 2cy LBBG of unknown origin and with adult argenteus Herring Gulls.
image 4: with LBBG of unknown origin (but average grey-tone in the Netherlands) and with adult argenteus Herring Gull.