|Flight feather molt similar to many of our northern hemisphere gulls in September.|
The species reminds me most of Laughing Gull, especially bill size and proportions (but perhaps with a slightly larger body). The voice is unlike any gulls I know but the quality is nasally.
In a recent interview I did with Birding magazine, I commented that Mediterranean Gull or Gray Gull would be the next ABA gull for our area. My prediction is that Gray Gull will occur first with recent records creeping into Central America. There is a disputed account from Louisiana (December 1987) of a bird that may or may not have been that species (interestingly, a melanistic Laughing Gull wasn't clearly eliminated - a photo can be found here).