What is "swamp harrier"

The swamp harrier (Circus approximans) also known as the marsh harrier, Australasian harrier, kāhu, swamp-hawk or New Zealand hawk. It is large, slim, and the most common bird of prey in New Zealand countryside. It is one of the few birds to have benefited from European-New Zealand settlement: It is a bird of open country and became firmly established after forests were cleared by Polynesians.

The swamp harrier belongs to the sub-family Circinae and genus Circus, which are represented worldwide, except Antarctica. The sub-family and genus are derived from the characteristic behavior of circling flight during courtship and hawking.