The shape of the streamers may not be easy to judge and just because you don't see the spoon-shape don't call it a Parasitic on this mark alone. Pomarine Jaegers are larger than Parasitic, about the size of a Herring Gull. They are often often heavily barred below. The breast band is broad. Look for Jaegers on the Gulf of Mexico from Late August though April.
Jaegers breed on the high tundra and winter at sea.