Adult Steppe Gull (Larus (c.?) barabensis).
This is a bird nearer the dark extreme for the outer wing:- black
to P3; black on P5 extends well up outer edge; no gray tongue
visible on inner web of P8 (nor apparently on P7, but it may be
hidden in this view); black lines on the outer primary coverts;
smallish mirror on P10 that is well-separated from the tip (no
mirror on P9). Note the fairly pale eye and indistinct blackish
mark near the tip of the bill: