How to spot a native: Ruru

Try doing this with your mouth (just the vibration rolling the rs with no voice): "Frrrrrrrrrt! Frrrrrrrrrrt!"

If you go into the bush in the early evening or sometimes late afternoon in January, you'll hear that sound. If you quietly follow it, you'll find a baby owl which is big enough to leave the nest with most of its feathers but hasn't got enough voice yet to call "ruru" or "morepork" or to feed itself.

Owlets can be quite insistent with their calls and parent birds will be silently and swiftly flying back and forth with beetles or some other snack for the demanding young ones. Sometimes you can hear other little birds freaking out because they don't want to end up on the menu.

If you're lucky, you'll see those owlets rotate their heads 270 degrees to look behind them. They have extra neck vertebrae for that. Chicks also do loops with their heads, then turn their heads 90 degrees to look like carved Maori ancestors in a wharenui.

Ruru feathers are dark brown and beautifully mottled up close, and designed to make flight silent.

I stood with friends last summer watching parent owls with beetles in their beaks fly centimetres above our faces to feed the two owlets. We felt the air movement but couldn't hear the sound of wings even though we were so close.

Ruru nest where it is dry. Often it will be in an old tree where a branch has broken off, rotted and left a hole. But they don't mind having nests close to the ground, sometimes under logs. A keen birdwatcher in the Bay of Islands has even filmed a ruru nest in the side of a stream bank where a kiwi stomps in to have a nosy (see lowdown).

As the sun goes down, the night shift of native forest life begins. Ruru are birds of prey, eating what they hunt and kill. They hunt by sound and sight. They listen for movement, which might be the rustle of a lizard or insects in the leaf litter or a bird fidgeting. Their huge eyes have big pupils that let in light for them to see as far as possible as they soar towards the prey.

The first kill of the night happens as the day birds are going to sleep and is usually a small bird. Throughout the night, ruru will eat weta, large moths, lizards, beetles and occasionally mice. They crush and carry prey in their talons and scoff it down. About 12 hours later, whatever can't be digested, usually feathers and bones, are vomited up. These are rather nicely called "casts".

Although you might expect owls to be the unchallenged top of the night food chain, introduced mammals were key to the extinction of whekau, the laughing owl, which was nearly twice the size of ruru and the largest flying night predator of these islands. Within 50 years of the introduction of stoats and ferrets, whekau was gone, though rats, weasels and cats probably played their part too.

There's an important point here: if we keep introduced predators to very low levels, we could have ruru all through suburban areas because they are very adaptive birds.

Plans to build ruru nesting boxes are at wingspan.co.nz