Photo 11: LBBG intermedius sub-adult, June 17 2001, Naaktstrand Maasvlakte, the Netherlands. 

The primaries are jet-black and show no white tips and just an extremely small faint mirror on p10 (visible in the field).
Moult in the upper-parts is advanced: the scapular coverts show a white tip but are old anyway. In the lowest row of the scapular, several fresh dark grey feathers have grown in recently. The tertials and the coverts are a mix of brown and grey feathers and active moult is going on in the central median coverts.
The bare parts are very adult-like: legs are lemon yellow, the red spot confined to the lower mandible and the small black spot on the upper mandible is hardly visible. The under-parts are snow white.
This appeared to be a remarkable small individual, with only the size of Common Gull, Larus canus.