Réunion Kestrel

Known from subfossil bones and the writings of Dubois published in 1674, this bird was larger than its relative F. punctatus on Mauritius, being about the size of a common kestrel, or around 35 cm from head to tail, with males being noticeably smaller than females. This trait, while present in most birds of prey, is most pronounced in the larger, bird-eating species and reduces between-sex competition by niche differentiation. It can be assumed that the bird was of the same generally brownish coloration as its closest relatives, with a lighter underside and darker spots or stipples, the tail, brown or more probably grey, being banded and tipped black. Its feet were yellow and large relative to the bird's overall size. The wingspan was 60–70 cm, its wings being more rounded than those of the common kestrel - just as in the Mauritius bird - for increased maneuverability when hunting in the forest. It is probable, but not certain, that the only difference between the sexes was their size.

The bird fed mainly on birds, but certainly also on insects and the Reunion Island day gecko (Phelsuma borbonica). Dubois noted that despite their small size they were able to prey on domestic chickens.