Magnificent Frigatebird (Fregata magnificens) over San Fernando Hill
Not seen frequently, but seen.
Quite possibly nesting on the hill; orientation of flight was Easterly toward the Gulf of Paria from limestone outcropping facing the Gulf.
In 'Birds of Trinidad and Tobago', Richard ffrench notes it in North Trinidad, as well as Tobago and notes that it nests on remote, undisturbed islands. Perhaps the key is undisturbed, or less disturbed. It may be infrequent in the environs of San Fernando Hill, but it is certainly here - and since its diet is fish, it seems unlikely that it is feeding this far inland.