Gull-billed Terns are medium size terns with heavy black bills and shallow forked tails. The upper parts are grey and the crown and nap are black (almost white with fine streaking in the winter). In a group of terns on the beach or flats look for their black legs.
Gull-billed terns don't dive like most terns. They are often seen over marshes hunting insects. Rarely seen in inland.
Look for Gull-billed Tern at Bolivar Flats Bird Sanctuary, Galveston Island State Park, San Luis Pass. and Brazoria NWR
A winter range map is available from the Christmas Bird Count