Swallow-tailed standing on brown, lava rocks on an island in the Galapagos. Its breading collors, the gull's head is black and the eyes red-rimmed. It is lovely grey and white shadings and dark swallow-tail are lovely against a background in shades of gray. Swallow-tailed gulls are the world's only fully nocturnal gull and seabird. The species is endemic to the Galapbaogs Islands and prey on squid and small fish.