A hard-won battle with the weather has enabled the Department of Conservation to strengthen the population of a threatened bird species.
After weeks of waiting on the weather, DOC and the Mohua Charitable Trust were this week able to transfer 22 mohua from the Catlins to Resolution Island in Fiordland.
The birds were captured in Eastern Southland by a team of 20 catchers and flown by helicopter to Dusky Sound. The Catlins mohua will join a population already established on Resolution Island to strengthen the genetic makeup.
Mohua are one of the rarest songbirds in the country and have recently been voted by New Zealanders as bird of the year, in the Forest and Bird's annual poll.
It was hoped Resolution would become a "genetic hotspot" for mohua and other threatened birds.
About 60 mohua were transferred from Landsborough Valley in South Westland in 2011.
DOC Te Anau biodiversity ranger Hannah Edmonds said October was the ideal time to try to capture the birds because they were pairing up and seeking to establish a territory.
"They tend to stay in the one area during this time," she said.
However, it was only on Wednesday, after weeks of waiting, that conditions were perfect for the operation, she said.