These pics were taken on December 20, 2006 in the Coastal Plain near Houston and Galveston, Texas; it appears to have all the features of first-cycle Vega Gull:
Note the underparts: instead of the brown wash (sometimes with slight smudging) common to all the large New World gulls, they are whitish with blurry barring on the lateral flanks and well-spaced streaking on the chest and sides of the belly, creating the impression of an almost unstreaked whitish area running down the center of the underparts; the white vent plus undertail coverts where the white bars a clearly larger than the dark bars combine to create an overall whitish rear- underparts.
Note on the upperparts: the uppertail coverts and rump with sparse dark marks such that it looks white;
thick white bands in base of tail; 2nd-gen scaps very pale-centered with neat double-anchor pattern; upperwing coverts with lots of white (including onto the patagial band of lesser coverts); tertials with worn-away notched white edging reaching to the visible bases; primary tips blackish (not brown of a possible hybrid):-
