as an Important Bird Area (IBA) by BirdLife International because of its significance as a seabird breeding site. Both masked (with up to 250 pairs) and red-footed boobies (up to 180 pairs) nest on the island. Sulidae populations have seriously declined in the western Indian Ocean with those on Tromelin among the healthiest remaining. The island's masked boobies are of the western Indian Ocean subspecies (Sula dactylatra melanops), of which Tromelin is a stronghold. The red-footed boobies constitute the only polymorphic population in the region, indicating its biogeographical isolation. Both great and lesser frigatebirds used to nest on the island. The breeding populations of both birds have since been extirpated, although they continue to use the island for roosting. There are no resident landbirds. History The island was discovered by France in 1720s. It was recorded by the French navigator Jean Marie Briand de la Feuillée and named “Île des Sables” (‘Isle of Sand’). Wreck of the ship Utile On 31 July 1761 the French ship Utile ("Useful"), a frigate of the French East India Company, chartered by Jean-Joseph de Laborde and commanded by Captain Jean de La Fargue, transporting slaves from Madagascar to Mauritius in contravention of Mauritian law, ran onto the reefs of the island. The ship had departed Bayonne in France with 142 men. After a stopover on Mauritius (then called the Isle de France), the ship embarked 160 Malagasy men, women, and children at Foulpointe, on the east coast of Madagascar, to bring them into slavery on Mauritius, despite the prohibition of trafficking decreed by the governor. A navigation error, due to the use of two conflicting charts, caused the vessel to wreck on the reefs of Tromelin Island (then called the Isle of Sand). The ship was a frigate, not a slave ship, and thus was not equipped with the shackles and chains usually found on slave ships. After the wreck, the crew and about 60 Malagasy people managed to reach the island, but the rest of the slaves, locked in the hold, drowned. The crew retrieved various equipment, food and wood from the wreckage. They dug a well, providing drinking water, and fed on salvaged food, turtles, and seabirds. Captain Jean de Lafargue lost his mind as a result of the wreck, and was replaced by his first lieutenant, second-in-command, Barthelemy Castellan du Vernet who lost his brother Leon in the shipwreck. Castellan built