Réunion harrier  (Circus maillardi)

Classified as Endangered (EN) on the IUCN Red List (1) and listed on Appendix II of CITES (3).

The Réunion harrier is the only raptor currently breeding on Réunion Island and has the smallest population of any bird species there (4). The male Réunion harrier has a predominantly black head and dark back, contrasting with light grey primaries and secondaries, and a white rump, belly and underwings. Female Réunion harriers are larger than males and have dark brown plumage with a barred tail (2). Immature Réunion harriers are similar in appearance to the female birds, while chicks are pale grey (5). This species has relatively short, rounded wings, which are thought to be an adaptation to hunting in dense vegetation, and a long middle toe which is typical of a bird-hunting specialist (6). The Réunion harrier can be heard making a grating kiay kioo near the breeding site, and the male calls with a kai pi-pi-pi-pi-pi during display flights (2).

The Réunion harrier is endemic to Réunion Island in the Indian Ocean (2) (6).

When breeding, the Réunion harrier nests in indigenous and degraded forests, between 300 and 700 metres above sea level (2). It forages in a range of habitats, but particularly in wooded and forested areas, as well as cultivated (sugarcane) fields and open grasslands and savannahs (2) (6).

The Réunion harrier feeds mainly on small vertebrates such as frogs, reptiles, rats, birds, shrews and insects. It hunts by flying low over vegetation and dropping onto its prey below. With impressive dexterity, the Réunion harrier is known to pass prey to mates and young whilst in flight (6).

Réunion harriers are polygynous (6), meaning that males have more than one female partner. Male Réunion harriers start to perform twisting aerial display flights between August and September, accompanied with calls, in order to attract a mate (4). Females usually lay two to three eggs in a nest of grass and weed stems on the ground or in low vegetation between December and May. The eggs are incubated for 33 to 36 days and the young fledge after 45 to 50 days (5), remaining with the parents up until October (4).

The Réunion harrier is one of the rarest raptors in the world (4). Habitat loss is the main threat to this bird (2), with the island it inhabits losing 75 percent of its native vegetation cover since 1946 (7). Cultivation and urbanisation have eliminated native forest from all but the steepest of slopes (2), and the high level of human population growth and economic development on Réunion Island has resulted in an increase in urbanisation, road construction and tourism, causing further habitat destruction (2) (4). The natural habitat is also degraded by exotic plants, making the land more susceptible to the impacts of cyclones, heavy rains and fires (2).

Compounding the threat of habitat loss is hunting; poaching and persecution continues, despite protective legislation, as the Réunion harrier is locally believed to predate on chickens (2). Other possible threats include agricultural pesticide use and human hunting pressure on some prey species (2).

There are a number of protected areas on Réunion Island and it is vital that the remaining suitable habitat for the Réunion harrier is protected from further degradation and that public awareness campaigns are developed in order to stop poaching and persecution (2) (7). Population trends need to be monitored and ecological research is required to determine the effects of forest clearance and aid conservation plans (2).

For further information on the Réunion harrier see:

• BirdLife International:
  www.birdlife.org

• Endemic: a species or taxonomic group that is only found in one particular country or geographic area.
• Indigenous: a species that occurs naturally in an area.
• Polygynous: animals in which males have more than one female partner.
• Primaries: in birds, the main flight feathers projecting along the outer edge of the wing.
• Secondaries: in birds, the shorter flight feathers projecting along the inner edge of the wing.
• Vertebrates: animals with a backbone.

1. IUCN Red List (December, 2007)
   http://www.iucnredlist.org
2. BirdLife International (August, 2008)
   http://www.birdlife.org/datazone/species/index.html?action=SpcHTMDetails.asp&sid=30003&m=0
3. CITES (December, 2007)
   http://www.cites.org
4. Simmons, R.E. (2000) Harrier’s of the World: Their Behaviour and Ecology. Oxford University Press, New York, U.S.
5. del Hoyo, J., Elliott, A. and Sargatal, J. (1994) Handbook of the Birds of the World. Volume 2: New World Vultures to Guinea Fowl. Lynx Edicions, Barcelona.
6. Bretagnolle, V., Ghestemme, T., Hiollay, J.M. and Attie, C. (2000) Distribution, Population Size and Habitat Use of the Reunion Marsh Harrier, Circus M. Maillardi. Journal of Raptor Research, 34(1): 8 - 17.
7. Mittermeier, R.A., Gil, P.R., Hoffmann, M., Pilgrim, J., Brooks, T., Mittermeier, C.G., Lamoreux, J. and Da Fonseca, G.A.B. (2004) Hotspots Revisited. CEMEX, Mexico City.