The Question: A seabird showed up every day to circle our sailboat 200-300 miles northeast of the Bahamas. One day there were 3 of them, but most days there was just one. It looked ‘gull-like’ and was very white with striking black trim around the trailing edge of his wing feathers. The tail is long and string-like in appearance (versus a fan of feathers). What bird is this?
The Short Answer: Ed, your photos and description are perfect for a tropicbird. The long trailing tail is a giveaway. From your photo and the locality, I would guess that what you saw is a White-tailed Tropicbird (Phaethon lepturus), the smallest of the world’s three tropicbirds, with a wingspan of about three feet (94 cm). The other possibility would be the Red-billed Tropicbird (Phaethon aethereus), which is a bit larger, with a wingspan of 44 inches (112 cm). The Red-billed Tropicbird flies with shallow wingbeats and even at some height, the red bill is fairly visible. So unless you saw either of those clues, I feel pretty comfortable identifying your birds as White-tailed Tropicbirds.
More Info: The White-tailed Tropicbird spends most of its life flying over the ocean, eating fish and squid off the surface. Their best trick is catching flying fish on the wing … or on the fin, to be more accurate. The White-tailed Tropicbird is found throughout the tropical oceans of the world.