Heuglin's Gull or Siberian Gull is sometimes considered as a separate species (Larus heuglini) and sometimes as a subspecies of Lesser Black-backed Gull (Larus fuscus heuglini).
The head and body of Heuglin's Gull is often very white, with streaking restricted to a neat necklace on the lower, rear neck.
Compared to other subspecies of Lesser Black-backed Gull, many Heughlin's Gulls look rather elegant, with a small head, long, contourless bill, long neck and long legs.
This combination of features can give some Heuglin's Gulls more than a passing resemblance to Caspian Gull (Larus cachinnans).

Salalah Beach, Dhofar Region, Oman, 2 & 9 February 2017