Swamp Harrier

Circus approximans - Busard de Gould

Id. Record English version

Geographic range

Pictures

Swamp Harrier

Circus approximans

(Peale, 1848)

Order : Accipitriformes

Family : Accipitridae ;

Genus : Circus

Species : approximans

Monotypic species

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Biometrics :

Size : 53 à 65 cm
Wingspan : 1,10-1,60 m
Weight : 500-700 g (M) - 700-1100 g (F)

Longevity : 18 years

IUCN conservation status :

Extinct

Threatened

Least
concern

Extinc
in the Wild

Near
threatened

Not
evaluated

EX EW CR EN VU NT LC NE

Geographic range :

Synonyms : moták tichomořský (cs), Australsk Rørhøg (da), Sumpfweihe (de), Swamp Harrier (en), Aguilucho Lagunero del Pacífico (es), australiansuohaukka (fi), Albanella australasiatica (it), ミナミチュウヒ (ja), Australsivhauk (nb), Australische Bruine Kiekendief (nl), błotniak moczarowy (pl), Болотый лунь (ru), kaňa barinná (sk), Australisk kärrhök (sv), 沼泽鹞 (zh)

Physical description :
Females are larger than males. Adults have a light grey head, cheek, nape and hood. The upperparts all the way to the tail is presents different hues of brown. However the scapulars and the mantle tend toward a rufous-orange colour. The underparts are white with fine brown streaks. The feathers covering the thighs are orange or pale brown. The undertail coverts are grey and slightly barred. The eye is yellow, as are the legs. First-winter juveniles have brown eyes, a dark brown plumage with an obvious white nape. As they get older, the eye and plumage get paler. Some older birds can even appear greyish-white.

Habitat : The Australasian Harrier is a specialist of open country and sparse vegetation, and is found from sea level to an altitude of 1,200 meters. In Australia it is confined to fresh and saltwater wetlands and is commonly found in marshes with high or low vegetation. In New Zealand, it is found in cultivated areas, pastures, plateaux and wooded valleys. The diurnal raptor is endemic to the West Pacific (Papua-New Guinea, Australia, New Guinea, New Zealand and outlying islands (Lord Howe, Macquarie, Kermadec, etc.) Another subspecies is found in the Pacific Islands Fiji, New Caledonia, Vanuatu.

Behaviour : All year round, the Australasian Harrier patrols its territory in search of food. It flies over the countryside, circling effortlessly during long hours. It follow air currents, alternating between gliding and beating its wings. It is frequently mobbed by other species, especially the Spur-winged Lapwing which will harass harriers until they turn tail.

Reproduction-nesting : The long breeding season starts in June, when pairs patrol their territory together to ward off intruders. During the warmer days from July to October, both partners carry out acrobatic display flights punctuated by powerful calls. From September, females start building the nest, usually a low platform principally made of fern, manuka and rushes covered by straw, legumes, grasses and leaves. The nest can be built in diverse spots: on the ground in a marsh, in a wetland dominated by rushes, in bracken, in a grassy area, in a young pine plantation or a road verge. It is rarely found on the fork of a branch. Pairs reuse the same sites year after year.

The female alone incubates the 1-7 eggs while the male provides her with food for the 31-34 days of incubation. She also feeds the chicks with the preys that the male brings back. When the chicks are old enough both partners hunt and if the male is alone when returning to the nest, he will drop the food in but will not actively feed the chicks. 2-3 weeks later, the young harrier leave the nest and spread out in the nearby vegetation. They will only fly after 45 days, but stay around the nest and call repetedly until one of the adults provides them with food.

Food habits : Although it capture most of its prey on the ground, this raptor seems to have developed a knack for capturing birds perched at the top of trees or sometimes even in flight. In New Zealand, the Australasian Harrier targets mainly aquatic birds that nest on its territory: young Pkkeko (Purple Swamphen) and ducklings pay the highest tribute. Wild Turkey eggs are also a prized delicacy, especially when then are close to hatching. However, the majority of its diet comes from scavenging on sheep carcasses or roadkill - small marsupials, rabbits and hares, hedgehogs or porcupines.

Sources :

IOC World Bird List (v3.1), Gill, F and D Donsker (Eds). 2012.
IOC World Bird List (v3.1), Gill, F and D Donsker (Eds). 2012.