Environment – Lord of the dance

My garden looks onto a swamp with a straggly covering of ti tree. The margins and banks are pretty wrecked from cattle that graze the stream, but, as the corridor links to mature bush in one direction and larger rivers in the other, there’s a massive amount of birdlife. Because it is scrubby with reeds and open pasture, it is just the right environment for kahu or harrier hawks. I can always tell when the kahu are reeling (sky-dancing) above, from their calls, the aerial sorties of the magpies and spurred lapwings (plovers), and because the chooks turn their eyes up to the sky and have a distinct clucking response.

Our kahu are one of three types of New Zealand birds of prey, and the largest of the world’s 16 harrier species. Because they thrive with forest clearance and agriculture, they are common and occupy most habitats across New Zealand, including widespread offshore islands. They are easily recognisable – big tawny, brown birds with a strong hooked beak, large taloned feet and yellow eyes. Their feathers lighten with each moult, so the ghostly grey bird that circles my valley is a senior kahu. Their Latin name, Circus aproximans, comes from their circling flight. Their body length is from 50-58cm, and their wingspan is 120-145cm. They weigh 580-1100 grams, though the female is considerably larger than the male.

Kahu nest on the ground or low bushes in bulky beds made from sticks, long grass and bracken in scrub and wetlands. They may build onto their nests from one season to the next. They sometimes use sun-warmed, carefully selected and strategically placed stones to keep their eggs warm while the female hunts for food. Their eggs are laid from October, maybe as late as February, and the female nests alone, caring for between two to seven, but usually three to four off-white eggs that take just over a month to hatch. The chicks are feathered in another month and fledging in about six weeks. In non-breeding seasons, communal roosts can host up to several hundred birds. The oldest known kahu lived to 18 years old.

It is estimated that Kahu self-introduced themselves to New Zealand about a 1000 years ago, so they’re native, and, despite bounties in the past, it’s mostly illegal to kill them. They can be a friend of farmers by eating mice and rabbits, as well as small birds, frogs and lizards. They only take prey on the ground, branches or ponds, not in the air. During winter when food is in short supply, they often eat carrion from the road. It’s this habit that does them most harm. My friends in Canterbury run Oxford Bird Rescue and have many kahu suffering from injuries, some fatal after being struck by cars. The best thing we can do to relieve harm and suffering, and allow a long life for this sky-dancing bird, is to remove carrion from the road.

Christine Rose
christine.rose25@gmail.com