NZ birds of prey / Native / Swamp Harrier
Why are Swamp harriers important?
The ‘kāhu’ swamp harrier is New Zealand’s largest bird of prey. This beautiful bird is most often seen lazily quartering over the open habitats that dominate modern day New Zealand. It is by far our most common bird of prey.
As carrion feeders harriers fulfil a vital role in our environment cleaning up all the animals that die on our roads and farms, as well as preying on vermin like rats and mice. As such, although the harrier is not a threatened species, it is important that we ensure they remain in healthy numbers. Without harriers New Zealand would be a far smellier place!
What other names does the Swamp Harrier have? Scientists call it: Circus approximans. Māori have many names for the Swamp Harrier including: kāhu, kōrako and kērangi. Others know the harrier as the hawk or Australasian harrier.
What do Harriers Eat?
Harriers are opportunistic and will take both live prey and carrion. During the spring and summer months they will feed mostly on live prey, whereas during the colder months, road kill, afterbirth and dead lambs are commonly fed upon. Young hawks often feed on insects, hunting for them by chasing and footing them on the ground. Once they are more confident fliers, harriers will also hunt by dropping onto unsuspecting prey with their long legs outstretched. Small mammals, birds and lizards are commonly taken in long grass in this manner.↑
Where can you find harriers and where do they breed?
Harriers are common throughout the open landscapes of New Zealand and Australasia. They naturally colonised New Zealand from Australia some 800 years ago after large areas of the country were cleared of bush during human settlement. Harriers generally nest in swamps and in areas surrounded by water to reduce access by predators. They will also nest in rank grassland, areas of cereal crop and in young pine plantations where they make a large nest platform out of grass and sticks. Very occasionally they will also nest in trees.
Pairs begin their characteristic ‘sky dancing’ courtship display in July/August. During this display both birds of a pair rise on thermals high into the sky, dropping down in a spectacular rocking dive, then looping back up high, sometimes completing large circles in the sky. This spectacular circular display flight is common in harriers around the world and is where their genus name Circus (which is Latin for circle) comes from.
Harriers lay between one and seven off-white eggs with the female doing all of the incubation. The male usually does not bring food directly to the nest but passes it to the female in their air by dropping the prey for her to aerobatically catch and take back to the nest.
Almost uniformly dark brown chicks fledge the nest between December and February. They become independent of their parents soon afterwards. Due to their naivety and inexperience these young birds are not as wise to the perils of feeding on road-kill as the adults. As a result many birds are handed into Wingspan for rehabilitation after colliding with cars during the autumn/winter months.↑
What does a Harrier sound like?
'Kāhu' swamp harriers are usually heard calling during the breeding season (starting in July), especially during courtship when they make a loud "keeuw" call. Listen to the calls of a juvenile made while feeding.↑
Can you tell the difference between a harrier and a falcon?
Five ways to tell the difference between a harrier and a falcon:
1. The falcon is usually seen in active hunting flight, chasing small birds with rapid wing beats; whereas the harrier is mostly seen gliding over the ground searching for carrion and small prey.
2. Harriers glide with wings set in a shallow dihedral V-shape and rock slightly in the changing air currents. Falcons glide with a very flat wing either very close to the ground trying to surprise prey, or very high in the sky as they survey their surroundings.
3. Harriers are often seen feeding on road-kill. Falcons almost exclusively take live prey and are very rarely seen on the side of the road.
4. Harriers have a large 1 metre wingspan and stand around 50cm tall. Falcons have a much shorter wingspan and are much smaller (about the size of a magpie).
5. Falcons and harriers differ in their plumage and colouration (see photos below).
Are harriers protected?
The legal protection of harriers has recently been downgraded meaning that it is now legal to kill harriers if they are causing injury to livestock or damage to property. This downgrading includes allowing conservation managers to cull harriers if they are perceived to have a negative impact on a threatened species. However, the evidence indicating that harriers have a negative impact on livestock is scarce and it is still not clear whether controlling harrier numbers to support threatened species programmes is practical or even successful (harriers are at such high densities in some areas that as soon as one individual is killed another will replace it immediately – in fact it could be argued that by removing a territorial pair a higher density of harriers could result). The decision to cull these beautiful birds should be based on fact. Wingspan advocates that more research be undertaken and is strongly opposed to the inhumane trapping methods sometimes employed to control them. These wonderful birds demand respect and above all their ‘control’ must not be taken lightly.
Want to learn more?
Then check out our PDF list of key references for more information and visit us at the Wingspan National Bird of Prey Centre in Rotorua to see these wonderful birds up close and learn about them from our expert staff.