The Mascarene Black Petrel (Pseudobulweria aterrima) is only known from four specimens found in the nineteenth century on the island of Réunion. Two birds were found dead in the 1970s, and there have been rare observations of birds in the waters south of Réunion since 1964.
This species is classified as critically endangered as it is inferred from the number of records that there is an extremely small population threatened by introduced species and light pollution.
This is a medium-sized gadfly petrel, averaging 36 cm in length. M The plumage is dark chocolate-brown with slightly paler chin, upper throat and underwing. It has a black bill, black feet, and webs with pale patches towards the base of the inner webs.