"Stop!" cries Matt, our guide, in a loud stage whisper.

I reel to a halt as something darts across the path in front of me, so close I nearly step on it.

"What was that?" come the whispers of the group behind me as the creature careers off through the bushy undergrowth.

"A kiwi," replies Matt. "Listen."

A shrill, undulating call vibrates through the just fallen darkness.

"That's the male kiwi," says Matt.

Its sharp, repetitive trill rattles through me. It can't be more than a few metres away.

Here at the Karori Sanctuary, just 2 kilometres from Wellington city centre, there are at least 80 of these Little Spotted Kiwi living inside the 252ha fenced area. Still, sightings are not guaranteed - even on a Sanctuary by Night Tour such as this.

"Basically, there are four kiwi areas where we'll be walking tonight," explains Matt as we set off.

"Each of these areas is about the size of a football field and we'll be walking down the middle of those football fields hoping we encounter a kiwi.

"So obviously, there's a lot of luck involved."

At Karori Sanctuary it's all about being in the right place at the right time. The sanctuary is just that - a sanctuary. It's not an aviary or a zoo, and as such, birds are living as they would in the wild. Those that can fly are free to come and go as they please. It seems that most choose to stay, feeding and breeding within the confines of the sanctuary's 2.2m high, 8.6km long predator-proof fence.

The fence, completed in 1999, was specifically designed to keep out mammalian predators, including mice, possums, stoats and cats. Before the fence's construction, the Karori Reservoir Valley's native bird population had dwindled to just 12 species. Following the completion of the fence, nine months of pest eradication began. Today, the sanctuary houses over 30 species of native bird and reptile, including tuatara, saddleback, hihi and weka.

"There are reports now of kaka and tui in Wellington city," says Matt, reiterating the success the sanctuary has been enjoying. The thought of such precious - typically rare - native birds frequenting our busy capital city is astounding.

We march on, determinedly, in single file, listening intently, ready for Matt to stop suddenly at any point.

Days of rain have produced a low fog that lurks above the sanctuary's tall podocarp trees, eerie in the waning light.

As the darkness intensifies, my other senses become enhanced. I smell the ever-changing scent of the surrounding native bush: sweet, raw, earthy, and dense. It moves with the breeze and washes over me in waves.

I feel the crunch of every stick and every piece of bark beneath my feet on the soft forest path.

Silver ferns tickle my hands - wet and scratchy as I brush by.

Every squeak and click of the katydids, the warble of moreporks and the purring of pateke (brown teal) is amplified.

I see the illuminated dots of glow worms clinging to mossy banks of earth. We stop at one bank and the effect is like staring at a sprawling, far away city of twinkling green and blue lights.

Then I hear the unmistakeably piercing cry of a kiwi. We stop collectively, daring not to move or breathe. The call comes again, insistent. Then there is another, this time the female call, identifiable by its distinctly deeper sound.

"They're looking for one another," says Matt when the calls have subsided. "They're saying to each other, 'hey, where are you?', 'I'm hanging out down by the worm pit', 'what time do you want to meet up tonight?' and things like that."

Just knowing we are in the vicinity of these beautiful rare birds is almost as exciting as seeing one. When Little Spotted Kiwi were introduced to Karori Sanctuary in 2000, it was the first time they had been present on mainland North Island for over 100 years.

The Little Spotted Kiwi is the smallest of all kiwi species and, like its larger relatives, does not fare well against vicious predators like stoats, cats, ferrets and dogs. The Little Spotted population was dwindling significantly before predator-free sanctuaries, like Karori and nearby Kapiti Island, were established. Now there are thought to be around 1600 Little Spotted Kiwis in the world. Whilst encouraging, this is still a precariously low number, which makes hearing or seeing one all the more special.

We trudge along behind Matt, up winding paths, across footbridges and under overhanging fern fronds, with ears on high alert. The suspense becomes as thick as the humid night air.

Emerging from the shelter of the forest we arrive at the 'top dam'. All I can see is two long, white, curving hand rails which seem to glow in the darkness. This dam was constructed in 1908 and is one of only a handful of gravity arch dams (a name that refers to its shape and construction style) in New Zealand. One of two built as part of Wellington's city reservoir under the Wellington Waterworks Act 1871, the dam now provides a lake haven for the sanctuary's winged residents.

Walking across the dam, tiny, misty specks of rain fly about my face. Far below a duck splashes and quacks. I cannot see it, or the water, through the darkness. In fact, I can see so little that the effect is like floating in the thick, fresh air. The silence tells nothing of the bustling capital city sitting just 2 kilometres away.

In the 15 years since the idea for Karori Sanctuary was coined, enormous change has taken place in this peaceful valley. The development and regeneration so far is but a seed in the forest that is the sanctuary's 500-year vision. The hope is that in 500 years time, the area will be representative of an indigenous lowland forest. It will become 'old New Zealand' for generations, and generations to come.

Amelia visited Karori Sanctuary courtesy of Positively Wellington Tourism and www.fourcorners.co.nz.

The Sanctuary by Night Tour operates every night of the year. Bookings necessary.