This first-cycle gull looks like a candidate Slaty-backed Gull Larus schistisagus. It was photographed at the new Corpus Christi Landfill south of town in Nueces county, Texas on February 03, 2011:
Note the following features which suggest Slaty-backed Gull:-
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the very pale plumage for a first-cycle large gull (looking more like some second-cycle Herring Gulls)
- the rather wide stance of the short legs plus a bit of a pot-belly and a long neck impart a somewhat goose-like pose when the bird is alert
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the white foreneck extending onto the chest and upper breast
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the frostiness of the markings on the sides of the belly and flanks
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the stout but evenly-edged bill and the rather small, beady eye
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the warm tone to the head/rearneck markings
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the folded primaries are pointed and brown (same color as distal part of tail) with thin pale fringes
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the plain pattern of the brown, worn first-generation tertials (simple pale pand at tip)
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the large pale band near the tip of the fresh 2nd-generation lower scaps
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the scattering of small pale spots on the dark bases of R3 - R5 (from above) on the tail
- the contrastingly pale rump/utcs compared to the tail, in flight from above
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the soft transition (from above) from darkish to paler, parallel to the shaft, on the outer primaries
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the pale on the inner webs of the dark secondaries (from above) forming a "venetian blind effect" when these feathers are slightly spread
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the strong dark tips to all the primaries from below and the silvery-pale tone of the entire primaries from below (apart from the dark tips)
Note the following features not typical of "classic" Slaty-backed Gull:-
- the extent of pale in the bill base - although a reasonable minority of first-cycle SBGUs can have bills patterned like this in February
- the rather contrasting pattern of thin dark "anchors" in many of the 2nd-generation scapulars - but photos of birds with this pattern are not hard to find
- the greater secondary coverts are not significantly paler than the rest of the coverts
- again there are photos of birds that lack this pale band in February
