The Swamp Harrier (Circus approximans), also known as the Marsh harrier, Australasian Harrier, KÄhu, Swamp-hawk or New Zealand Hawk, is common through Australasia and many islands in the south-west Pacific region, including much of Australia (except the arid region), New Zealand, Vanuatu and New Caledonia. It is usually found in wetlands and well-watered open country.
It is a large, slim bird with a body length of 19.6 to 23.6 inches and a wingspan of 47.25 to 57 inches. Adults weigh from 20 to 39 ounces. Females are much larger than the male. It is dark brown in color, and lighter as it ages. It has a distinct white rump. It hunts by flying slowly, near the ground, on upswept wings. It mainly feeds on ground birds and water birds, small mammals, reptiles, frogs and fish.
This species nests on the ground, often in swamps, on a mound in reeds or other dense vegetation. The clutch size may range from 2-7, but is usually 3-4. The incubation period is about 33 days, with chicks fledging about 45 days after hatching.