The bird never stood with its neck drawn in like the bulky short necked, large headed, red billed Caspian Terns' usual stance. In flight this bird appeared slim, lighter more fluid of motion, the upperwing was pale with only slightly darker color to primaries, underwing showed pale pimaries with narrow dusky trailing edge.

I ruled out the South American Large-billed Tern by size, Crested Tern by color, Lesser Crested Tern by size, Elegant Tern by bill color, length and shape, crest length, plus leg length.