'I said, "What did you say?"'

`I just said, "Do you come here often?" but let it pass.'

At last we lapsed into an awkward, deafened silence that was made all the more oppressive by the heavy bank of storm clouds that was hanging sullenly over the sea.

Soon the sombre bulk of New Zealand's most fiercely protected ark loomed up out of the shining darkness at us: Codfish Island, one of the last refuges of many birds that are hardly to be found anywhere else in the world. Like Little Barrier Island it has been ruthlessly purged of anything that was not originally to be found there. Even the flightless weka, a fierce and disorderly duck-sized bird, which is native to other parts of New Zealand, has been eradicated. It wasn't a native of Codfish, and it attacked Cook's petrels which were. The island is surrounded by rough seas and strong currents, so no predator rats are likely to be able to make it from Stewart island three kilometres away. Food supplies to island workers are stored in rat-proof rooms, packed into ratproof containers, and rigorously examined before and after transfer. Poison bait is distributed around all possible boat landing places. There are people ready to swing into immediate fire brigade action to eliminate any rat invasion if a boat wreck occurs.

The helicopter came thudding in to land, and we clambered uneasily out, hunching ourselves down under the rotating blades. We quickly unloaded our bags and walked down and away from the tussocky hillock on which we had landed towards the wardens' hut. Mark and I caught each other's eye for a moment and we realised that we were both still hunched over as we walked. We weren't actually rats, but we felt just about as welcome, and we hoped to God that the expedition was not going to go horribly wrong. Arab stalked silently behind us with Boss who was now tightly muzzled. Although tracker dogs are rigorously trained not to harm any kakapos they find, they can nevertheless sometimes find them a little too enthusiastically. Even wearing a muzzle an over-eager dog can buffet and injure a bird.

The wardens' but was a fairly basic wooden building with one large room which served as a kitchen, dining room, sitting room and work room, and a couple of small dormitory rooms full of bunks. There were two other field workers already installed, the eccentrically named, or rather spelled, Phred, who turned out to be the son of Dobby and Mike, and also Trevor. They greeted us quietly and without enthusiasm and let us get on with our unpacking.

Soon we were told that lunch was ready, and we realised that it was time for us seriously to try to improve our general standing around the place. Clearly our hosts did not want to have a bunch of media trendies rampaging round their island frightening the birds with their video cameras and Filofaxes, and they were only slightly mollified by the fact that all we had was one tiny Walkman tape recorder, and that we were being very meek and wellbehaved and trying not to order gin and tonics the whole time.

The fact that we'd actually brought some beer and whisky with us helped a little.

I suddenly felt extraordinarily cheerful. More cheerful, in fact, than I had felt for the whole of our visit to New Zealand so far. The people of New Zealand are generally terribly nice. Everybody we had met so far had been terribly nice to us. Terribly nice and eager to please. I realised now that all this relentless niceness and geniality to which we had been subjected had got to me rather badly. New Zealand niceness is not merely disarming, it's decapitating as well, and I had come to feel that if just one more person was pleasant and genial at me I'd hit him. Now things were suddenly very different and we had work to do. I was determined to get these surly buggers to like us if it killed me.

Over our lunch of tinned ham, boiled potatoes and beer we launched a major conversational assault, told them all about our project and why we were doing it, where we'd been so far= what animals we had seen and failed to see, whom we had met, why we were so keen to see the kakapo, how much we appreciated their assistance, and how well we understood their reluctance to have us there, and then went on to ask intelligent and searching questions about their work, about the island, about the birds, about Boss, and finally, why there was a dead penguin hanging on the tree outside the house.

This seemed to clear the air a little. Our hosts quickly realised that the only way .of stopping us talking the whole time was to do some talking themselves. The penguin, Phred explained, was traditional. Every 28 February they hung a dead penguin on a tree. It was a tradition that had only started today and they doubted if they would keep it up, but in the meantime at least it kept the flies off the penguin.

This seemed a thoroughly excellent explanation. We all celebrated it with another glass of beer and things began at last to move along with a bit more of a swing. In an altogether easier atmosphere we set out into the forest with Arab and Boss to see if we could at last find one of these birds we had travelled twelve thousand miles to see.

The forest was rotten. That is to say that it was so wet that every fallen tree trunk we had to clamber over cracked open under our feet, branches we clung on to when we lost our footing came away in our hands. We slipped and slithered noisily through the mud and sodden undergrowth, while Arab stalked easily ahead of us, just visible through the trees in his blue plaid woollen windcheater. Boss described a chaotic orbit around him, hardly ever visible at all except as an occasional moving flash of blackness through the undergrowth.

He was, however, always audible. Arab had fastened a small bell on to his collar, which rang out clearly through the clean, damp air, as if an invisible and deranged carol singer were cavorting through the forest. The purpose of the bell was to allow Arab to keep track of where Boss was, and also to let him know what the dog was up to. A flurry of agitated rings followed by silence might indicate that it had found a kakapo and was standing guard over it. Every time the bell fell silent we held our breaths, but each time the clanging started up again as Boss found a new avenue in the undergrowth to plunge through. From time to time the bell would suddenly start to ring out more loudly and clearly, and Arab would summon Boss back to him with a quick shout. There would then be a slight pause, which on one occasion enabled Mark and Gaynor and me to catch up with them.

We came tumbling breathless and wet out of the forest to a small clearing, where we found Arab squatting beside Boss stuffing a small wad of mossy earth up into the cavity of the bell to dampen its sound a little. He squinted up at us with his slow shy grin and explained that the bell mustn't be too loud or it would only frighten the kakapo away - if there were any in the area.

Did he think there were any around? asked Mark.

'Oh, they're certainly around,' said Arab, pulling his fingers through his streaming wet beard to clean the mud off them, `or at least, they've been around here today. There's plenty of scent. Boss keeps on finding scent all right, but the scent goes cold. There's been quite a lot of kakapo activity here recently, but not quite recently enough. He's very excited though. He knows they're definitely around.'

He made a fuss of Boss for a few moments, and then explained that there were major problems in training dogs to find kakapos because of the terrible shortage of kakapos to train them on. In the end, he said, it was more realistic to train the dogs not to track anything else. Training was simply a long and tedious process of elimination, which was very frustrating for the dog.

With one last pat he let go of Boss again, who bounded back off into the bush to carry on snuffling and rummaging for any trace of the one bird he hadn't been trained not to track. Within a few moments he had disappeared from sight, and his muted bell went clanking off into the distance.