It surely looks like eighter a kelp or a cape gull as the mirror on p10 and broad trailing egde rules out GBB. But when is comes to kelp (dominicanus) vs cape (vetula) (considered conspecific by some) it gets more difficult. The white mirror is hard to use as a clear indicative, but the dark eye, the olive tigned legs and the appearent flat crown point towards cape gull. Other indications are the very dark back as you mention, but the lower mandible also shows an obvious angle at the gony spot, which points towards cape. Any more pics of this gull?

Silas

I've just uploaded two more pictures of the same bird. Both new pictures are of low quality so I'm not sure if they will be accepted by the netfugl admins.

I just read the paper by Olof Jönsson in the latest Birding World. It's evident that both Cape Gull(s?) and Great Black-backed Gulls are still present in the Khnifiss Lagoon. Access to the lagoon has also improved during the last year as there has been built a new visitor centre along the gravel road just before the old wardens house. Entrance is 10 DH. We paid 350 DH for a two hour boat trip on the lagoon.