The pair have come from the Isaac Conservation and Wildlife Trust in Peacock Springs, Canterbury, and will be housed in a large aviary with kaka and sacred kingfishers.
Rainbow Springs wildlife programme manager Mark Paterson said it was exciting, not just for Rainbow Springs, but for all of Rotorua.
"These are so rare, you never get to see them. For me, what's most exciting is having the opportunity to contribute to conservation of the species.
"Being part of Rainbow Springs is pretty cool because we have neat animals and species here.
"Having these guys here is next level for me, it's just fantastic."
Paterson said the whio would be left to settle in for at least a week, and the enclosure opened to the public after that.
Eventually there would be daily keeper talks and freshwater enclosure talks about whio, eels, koura and kokopu.
Department of Conservation whio recovery group leader Andrew Glaser said a unique trait of the whio was a black membrane on the end of the beak.
They used it to feel around the rocks, and it was soft and replenished itself, he said.
He said their feet were designed to fold behind a wide toe so they were very streamlined in water.
One of the whio that has arrived at Rainbow Springs. Photo/Stephen Parker
He said the decline in whio numbers was caused by land clearing, shooting, damming rivers and hunting.
Glaser said today's threats were introduced pests such as stoats, ferrets, cats and dogs.
Rotorua's pair were originally from Whanganui. They were collected as eggs, incubated and reared in captivity and were now part of the breeding release programme.
"It's a huge opportunity for us to bring these birds back to the North Island."
Glaser said bringing them to Rainbow Springs was a great opportunity to build the profile and awareness of whio.
"Knowing what Mark and Rainbow Springs' aspirations are for showcasing whio and how unique they are, to raise that profile and adding to that conservation is quite significant for us in the release programme."
Whio are a taonga species with strong cultural and historical connections for Māori.
The Department of Conservation website says people can help with the recovery of whio by reporting all sightings, including date, location and number seen.
