The upperparts are relatively dark, helping us narrow down our choices to Sabine's, Franklin's or Laughing Gull. The longer legs could help rule out Sabine's as this a short-legged species that often resembles a shorebird when viewed on land at a distance.
The semi-hood looks similar to the what one may see on a Franklin's in the non-breeding season. However, Laughing Gull can also show this half-hood (depending on how much of the hood has molted in - or out). Further, the white apicals on the primaries may tempt one to call this a Franklin's, but adult Laughings often show white tips to the primaries (especially in late fall/early winter when the feathers are renewed).
The narrow eye crescents, long legs and long wing projection all help identify our quiz bird as a Laughing Gull. Seeing the relatively thick bill with flat, sharply sloped tip, makes the identification much, much easier.
This adult was photographed in Volusia County, Florida on 24 January 2016.