This Lesser Black-backed Gull type individual was photographed at Brownsville Landfill, Cameron county, Texas on January 18, 2016. It has an unusual combination of features:
Ostensibly it is a "late" 2C or "early" 3C LBBG, but even when standing
the exposed primary tips look a bit odd, in that the tip of P6 seems to be a third-generation pattern while P7-P10 seem more like 2nd-generation feathers.
In flight the remiges can be examined, and reveal a mix of 2nd-gen and 3rd-gen
type feather patterns:
In the primaries P1-P6 are much too adult-like to be 2nd-gen feathers, while P7-P10 seem too plain (with a brown tinge) for 3rd-gen feathers - yet the difference in condition/wear between these two blocks seems slight.
In the secondaries S1-S8/S9 are clearly of a 3rd-gen pattern, as are the inner 2 or 3 plus the outer tertials. The inner tertials and central Ss have a 2nd-generation pattern, and the demarcation between the two apparent age-class blocks of feathers is distinct (i.e there is no gradual change in appearance through parts of the tract, as seen with a gradual replacement process). The 3rd-gen type secondaries seem very fresh, but the 2nd-gen type feathers do not seem to be heavily abraded.
All of this leads me to ponder if this individual has undergone an inserted partial molt of its flight feathers - ?: