She said that once the birds flew into the bush several of them began to sing.
"It was awesome, and it was such a historic moment as there's only two other places where the hihi have successfully been transposed onto the mainland.
"I think them singing to us like that is a good sign."
The hihi project, which has been led by former trust chairman Allan Anderson, had been underway for about five years ensuring the park met the standards set for the tiny birds.
"Today has been the fruition of that process. We've installed food stations and nesting boxes for them which has been done by volunteers, and we've had to ensure the're able to enter a disease-free environment.
"We had a delay about a year because one of the birds was diagnosed with salmonella, but after some testing we established that wasn't a problem. It still set us back for a while."
Ms Tennet said many local businesses and individuals had contributed, as had a Saudi crown prince, but more donations would be needed.
"We've attached little radio transmitters to some of them, that cost about $10,000, and we'll be using aeroplanes or helicopters to monitor where they go. All the ongoing costs will need to be met somehow and we're always happy to hear from people who want to help with money or time, even if it's just two hours a month," she said.