Birds of prey have populated many island groups throughout the Indian Ocean and far ranging migrants regularly visit the Mascarenes. Two genera are certainly known from Réunion and Mauritius, Circus and Falco, while a possible third genus awaits confirmation from the fossil record.
The Mauritius kestrel, Falco punctatus, was once considered the most endangered bird in the world with numbers down to 6 birds in 1974. However, it has now increased to 2000+ individuals, probably as many as the island’s current habitat can support. A morphologically distinct species F. duboisi inhabited Réunion until c.1770. Unlike the Mauritius kestrel that has rounded short wings, the Réunion kestrel lacked these and was similar to the Eurasian kestrel complex. It was reported to ‘do harm to the fowls of the inhabitants and the game of the island’and probably persecuted accordingly.
The Réunion Harrier Circus maillardi is extant but endangered on Réunion and also once occurred on Mauritius. Circus alphonsi, which was described from fossil remains collected on Mauritius is now extinct, but is considered conspecific with C. maillardi.
An enigmatic species called an ‘Emerillon (=merlin)’ was described by Dubois in 1674 as ‘although small, do not fail to carry away chickens and eat them’. The Emerillon may have been a resident wide ranging species or an endemic small hawk that is now extinct. Two small hawks, Eleonara’s falcon Falco eleonarae and Sooty falcon F. concolor are vagrants to Réunion.