Kahu / Harrier

(Circus approximans)
Also known as kahu, swamp harrier, marsh harrier
Native, self-introduced

Live: Common throughout New Zealand, including the offshore islands.

Habitat: Kahu are birds of open habitats, one of the few to have benefited from the clearance of native forests for agricultural use and roads. (Road kills provide a steady source of food.) Drainage of wetlands threatens their breeding grounds.

Diet: In the wild, small mammals, large insects, smaller birds, frogs, fish, lizards and eggs. Much of the prey is introduced. Carrion forms a large part of their winter diet.

Zoo diet: Mice, minced whole chicken and minced horsemeat daily plus vitamins.

Gestation: Between October and December, the female builds a nest usually on or near the ground in grassy native plants, e.g. toetoe. The nests are made of large leaves and plant material and lined with grass. Four eggs are laid, one every second day, and incubated by the female for 31-34 days. The male feeds the female by passing food to her in the air, which she then eats away from the nest. The female may cease incubating after the first egg hatches, limiting the offspring to one, but usually 1-3 chicks hatch. Larger chicks eat the most food and may eat weaker or dead siblings. The youngsters fledge at about 45 days.

Status: Common

General: Females are larger than males.

Their call is loud, long and mournful, especially during the breeding season.

Although often seen alone, harriers may roost or hunt in large flocks depending on the season. Pairs and trios may also hunt together.

Flight is slow with periods of gliding, and soaring on thermals conserves energy.

Courtship involves display and breeding prompts territorial behaviour.