Slender-billed gull: Larus genei - Adult in breeding plumage.
Canon EOS 1D Mark IV, Canon EF 400mm f2.8 L IS USM, EF 1.4xII, ISO 800, 1/2500, f9, full frame image, Minor processing in lightroom.
Sharing some information from Birds of South Asia, The Ripley Guide by Pamela C. Rasmussen and John C. Anderton
A medium sized, slender, very pale gull, small-headed with a peculiarly long bill and elongated face and neck; appearance varies from rather normal to bizarre. Breeding adult has entirely white head, white iris and red bill, and a pinkish tinge below. Non breeding adult has faint dark ear-smudge. Juvenile has mostly pale pinkish bill and legs, dark eye and dark markings on mantle and upperwing-coverts. First-winter retains dark bar on wing-coverts above, with a dark basal secondary bar joining dark inner primaries, and mostly white outer primaries and wrist; tail has black band on distal third. In flight, very pale, and tail may look relatively broad; adult has wing-tip pattern of common black-headed.
Occurs: Summer visitor (or resident) SW and E Afghanistan (Seistan, Lake Ab-i-Estada, Kabul); resident Pakistan coast (breeding sporadically along Mekran Coast) and Gujarat, straggling in winter along W and SE Indian coast; vagrant Sri Lanka (one record, off tip of Mannar). A few occur as passage migrants, vagrants or winter visitors inland, from Indian Punjab to SE Nepal. Locally common, breeding at large shallow saline lakes, as well as by coastal lagoons and marine inlets; winters primarily in estuaries, tidal creeks and, rarely, inland at reservoirs; also well out to sea.
Habits: Wing-beats slower than in Common, and may fly in formation; often wades and forages in surf. Breeds in dense colonies May-Jun at Siranda Lake, Baluchistan coast, building a substantial nest; colonies subject to desertion if disturbed.