Groups of American White Pelicans flying in to congregate in the waters of John Bunker Sands Wetland Center in Seagoville, Texas.
Wikipedia has this to say about American White Pelicans:
The bill is huge and flat on the top, with a large throat sac below, and, in the breeding season, is vivid orange in color as is the iris, the bare skin around the eye, and the feet. In the breeding season, there is a laterally flattened “horn” on the upper bill, located about one-third the bill’s length behind the tip. This is the only one of the eight species of pelican to have a bill “horn”. The horn is shed after the birds have mated and laid their eggs. Outside of the breeding season the bare parts become duller in color, with the naked facial skin yellow and the bill, pouch, and feet an orangy-flesh color.