Jim Eagles discovers even our threatened species in sanctuary are not afraid to fight for territorial advantage.
We had only just set foot on Ulva Island when, from a clump of trees at the top of a bank, came the strident alarm call of a bellbird.
I went to see what was causing the excitement when out of the leaves burst a large dark brown ball of feathers that rolled to the bottom of the bank right in front of me.
When it stopped, the ball separated into two clumps of brown feathers: a weka and a morepork.
The morepork shook itself, flapped its wings clumsily and took off round the back of the wharf shed where it hid in a little crevice halfway up the bank. The weka spat feathers out of its beak and wandered nonchalantly off in search of food.
What on earth was all that about? "The weka would have been the aggressor," said Bevin Mudie, our guide from Stewart Island Experience. "That's why its beak was full of feathers."
But what was it doing? Trying to eat the morepork? Or just chase it away? "Oh, it would have just been to get the owl off its patch," said Bevin. "A lot of birds will attack owls if they get the chance."
At that moment, two brilliantly coloured tuis flew past, making a huge racket, seemingly shouting abuse and pecking at each other.
"Sometimes tuis will attack owls and chase them away," Bevin added. "They're seen as a potential threat and a rival predator."
That's presumably why the morepork continued to sit quietly in its dark little refuge doing nothing to draw attention to itself.
The incident mightn't have been much fun for the morepork but it was just about the perfect introduction to Ulva Island, off the coast of Stewart Island, a 250ha predator-free sanctuary where our native birds rule.
It was raining softly as we walked the island's network of tracks but that didn't stop a little South Island robin coming to check us out.
Bevin scratched the earth alongside the track and the robin quickly flew down to check if he had uncovered any insects allowing us to get a good look at the tiny bird.
"They're doing really well here," said Bevin. "There weren't any here originally. Then they released 20 and they've thrived. Now there are so many, they're able to send them to other sanctuaries."
As we continued our walk, he pointed out several tiny native orchids: a spider orchid, one with a delicate white flower and another that was greencapped. "You hardly ever see these elsewhere because they're one of the first things the possums eat."
Further down the track we were introduced to "the dinosaur plant", tmesipteris, the 400 million-year-old ancestor of modern plants, a survivor from the age of dinosaurs.
With a grin Bevin showed off a tree with a large glossy leaf said to make excellent writing paper - "the early settlers could use it to send letters home to mum saying they'd arrived safely" - and also suitable "for other paper purposes ... it's very strong like five ply".
A couple of metres away he pointed to a rangiora. "That's what they use for toilet paper in the North Island. It has a nice soft underside but it's not very strong and it tends to break up. So if you shake hands with a North Islander make sure you wash your hands afterwards ... are there any North Islanders here?"
That produced a bit of barracking but then Bevin asked us to walk quietly because on the next section of track there was a good chance of seeing some of the small bush birds.
A few moments later, he told us to watch a tree about 10m off the track where there was a rifleman's nest and, sure enough, there was one of the tiny birds bouncing cheerily along a branch, then a second one above it. "That's New Zealand's smallest bird. It grows to only 8cm and weighs only 6gm."
A bit further on, a small dark bird flitting high in the trees turned out to be a brown creeper.
We had heard several grey warblers singing in the bush - as well we might considering the weather - and then suddenly we saw one. Tiny considering the strength of its song.
Then followed tuis, bellbirds, a couple of red-headed kakariki, an immature yellowhead and, best of all, two beautiful South Island saddlebacks with their distinctive brown markings.
At the beach, which was the turnaround point for our walk, there were several weka, though these seemed more interested in checking out our bootlaces than crash-tackling passing moreporks.
As we walked, Bevin had pointed out several totara trees that had been damaged by kaka and several times he had seen them flying noisily overhead.
"They'll be heading to Oban" - the main town on Stewart Island - "for a feed", Bevin said.
"A lot of us put out sugar water, peanuts and maybe a few cashews to attract the birds."
And, sure enough, when we left Ulva Island and moved on to Oban, the township itself was full of birdlife.
In the course of a short walk, I spotted a fat kereru sitting on a powerline, a couple of bellbirds, a tui also resting on a powerline and lots of kaka.
But the highlight came at the Oban Police Station where a couple of kaka were busy feeding in the top of the hedge; one was sitting on the police house's chimney and three or four were on the deck evidently being fed.
One particularly bold kaka even jumped on to the arm of a man up there - presumably the local cop - and allowed itself to be handfed.
It was such an attractive scene that I didn't like to intrude. But I couldn't help wondering if the policeman knew he was entertaining a thief.
Maori legend has it that that kaka stole its beautiful red and green feathers from the kakariki and, to this day, hides them under its wings in the hope that no one will notice.
But I saw the colours clearly as the kaka flew overhead and I'm sure any kakariki would have recognised them too.
* Further information: Orion Expedition Cruises visits the Sub Antarctic islands, including Auckland, Campbell, Macquarie and The Snares, as well as Fiordland and Stewart Island, over the Christmas-New Year period. See orionexpeditions.com
Jim Eagles travelled to Ulva and Stewart Islands as guest of Orion Expedition Cruises.