Heavy snow has damaged two aviaries used to house the critically endangered black stilt (kaki) near Twizel.
More than 40 cm of snow caused one aviary to collapse on Thursday last week and another has been badly damaged and will have to be demolished.
Three of the 12 birds in the collapsed aviary are missing. The remainder were either caught again or seen nearby.
The wading bird is found only in the MacKenzie and Waitaki area.
Department of Conservation rangers worked in cold conditions to rescue 19 young birds from the second, damaged aviary. Temperatures reached minus 20 degrees on Monday night.
The department's services manager, Dean Nelson, said most of the hand-reared birds were safe, including the two breeding pairs, and the priority now was to get the birds out of the second damaged aviary.
Mr Nelson said the Isaac Conservation and Wildlife Trust had offered DOC the use of two spare aviaries at their facility at Peacock Springs in Harewood.
"It's too early to know the impact of losing two out three aviaries on the captive breeding programme but thanks to Isaac's we will get through this winter," he said.
Both of DOCs wooden-arch aviaries are nearly 30 years old and had been damaged previously with snow. A third and newer steel-arch aviary housing more than 40 young kaki was fine.