From tropical waters, "Longtails" travel up the Atlantic coast and nest in numbers on Bermuda Islands. I saw ten off Cape Florida in April following a school of small fish, sweeping, diving and chattering over and into the finny school. At the start of a nose dive the birds curved into almost a semicircle, tho this effect was only apparent when they were close enuf to perceive the thin tail feathers.
From Bermuda and adjacent Atlantic coast southward.