Réunion harrier

Specimen in Réunion Natural History Museum

It is about 42–55 cm long; the female is around 3–15% larger than the male.[2] The male has a blackish head and back with white streaks. The underparts, underwings and rump are white and the tail is grey. The wings are grey and black with a white leading edge. Females and immatures are dark brown with a white rump and barred tail.[3]

The birds are mostly silent except during the breeding season when they give a chattering threat call, a wailing courtship call and chuckling food-associated calls.[2]

The Malagasy harrier is larger and paler with longer wings and legs.

It is typically found in forested upland areas between 300 and 700 m above sea-level.[3] It also visits cane fields and grassland. Today its diet includes many introduced mammals (rats, mice and tenrecs) but it originally fed mainly on birds and insects.[3] It will also take small lizards, frogs and carrion.[2][3] It has a number of adaptations which are unusual among harriers: broad rounded wings for hunting between trees and a short tarsus and long claws, which are common among those birds of prey which feed on other birds.[4] It breeds between January and May and lays two or three white eggs in a nest on the ground.[3][5]

In 2011 it had an estimated population of at least 564 birds including about 150 breeding pairs.[3] It has been evaluated as endangered by BirdLife International and it is threatened by destruction and disturbance of its habitat and by poaching, deliberate persecution and accidental poisoning by rodenticides.[3] It became a protected species in 1966 and its numbers were thought to be stable or increasing until 2000–2010 when its population appeared to decrease.[3]

Sites identified by BirdLife International as being important for the conservation of the species are the Important Bird Areas (IBAs) of:[6]

• Mouth of the Cirque de Salazie
• Ravine de la Grande Chaloupe
• Rivière des Marsouins – Grand Étang
• Rivière des Remparts - Rivière Langevin

Sub-fossil remains of a Réunion harrier 9–10 and other birds from Mauritius

The species was described in 1862 by Jules Verreaux. He named it in honour of Louis Maillard, a French botanist and engineer who mentioned the bird in a book about the island.

In 1893 Alfred Newton and Hans Gadow described tarsometatarsi, tibiae and metacarpals from a hawk called Astur alphonsi (later renamed Accipiter alphonsi and Circus alphonsi) from Mauritius.[7] In 1958 James Greenway considered this taxon as conspecific with the pied harrier.[8] A later examination of the bones came to the conclusion that Astur alphonsi is actually identical with Circus maillardi, which formerly occurred on Mauritius too but is now extirpated.[9]