The Réunion owl (Mascarenotus grucheti) was a small owl that occurred on the Mascarene island of Réunion, but became extinct before living birds could be described; it is only known from subfossil bones. It belongs to the Mascarene owls of the genus Mascarenotus, and most likely was similar to a long-eared owl in size and appearance, but with nearly naked legs. The Mascarene owls were, however, more closely related to the genus Ninox. Compared to the Mauritius owl and the Rodrigues owl, it was the most terrestrial species of the genus, with long legs and possibly somewhat reduced flight capability; more probably though it was simply smaller than the Mauritius bird – between that species and the one from Rodrigues in size – but had equally long legs: the only suitable food available in quan