One or't 'tother

Another exercise in trying to replicate complex plumage patterns. This juv/1st winter gull at Old Moor one evening a month ago showed characters of either Lesser-black back or Yellow-legged. Although I didn't see it in flight I'm tipping the latter due to he rather 'med gull'-like head pattern. A quick dip into Malling Olsen (before my re-hashed drawing, ofcourse!)  would also suggest YLG but one of my vis-mig mates in Huddersfield who is red-hot with gulls has rightly said the book isn't much use at this time of year due to the huge variations which large gulls can show due to wear. This is a view shared by other experienced birders, I understand.  A proper look at the greater coverts and scapulars would have helped but, alas, I find it difficult to concentrate on both plumage and form when field sketching. If anyone can comment please feel free. Anyway, the beige Caran d 'Ache pencil works a treat for the young gull's ground colour!
Cheers
                                  
                                        Field sketch of imm gull, Old Moor, 17-09,14