New Zealand’s largest ever bird translocation project has been delayed because of a disease identified in some of the bellbirds caught on Tiritiri Matangi.

The project, which envisions restoring bellbirds to Hamilton after more than a century, is expected to go ahead once the birds have been treated with antibiotics.

The bellbird translocation project involved several agencies co-ordinating to capture and relocate up to 200 birds to four new locations. The birds were to be relocated from Tawharanui Regional Park in Auckland and Tiritiri Matangi Island to two sites on Waiheke Island, one on Motuihe Island and one in the Hamilton Gardens.

The Hamilton part of the project is being led by Landcare Research, the University of Waikato and Environment Waikato with the support of Nga Mana Toopu o Kirikiriroa, the Department of Conservation and Hamilton City Council. Bellbirds are commonly known as korimako to local Maori.

The release planned for May 9 in Hamilton was delayed after some of the Tiritiri Matangi birds tested positive for a bacteria called Yersinia. The disease is known to be present in some wild bird populations but has not been an issue in previous translocations. There are two strains of the disease. So far only the less severe strain has been identified in the Tiritiri Matangi birds.

"We were extremely surprised to find it but this is exactly why we do this precautionary disease screening," said Landcare Research’s John Innes,

"Yersinia is primarily associated with introduced rodents and birds such as sparrows and starlings and is probably found around Hamilton already. However, the released bellbirds might have died if they had been released without treatment.Yersinia occurs at a low incidence on Tiritiri Matangi Island but now that the birds captured for transfer are sharing aviaries, they are all being treated," Mr Innes said.

"The good news is that the capture of the birds and the complicated logistics all went very smoothly. We have 200 birds waiting in aviaries. Treating them with antibiotics is expected to take about a week and the releases will be rescheduled after the birds get the medical all-clear."

EW councillor Paula Southgate said she was pleased with how much public interest had been shown in the project and she thanked people who had come to the Gardens early on Sunday morning. "We were all disappointed but we had to do what was best for the birds."

Cr Southgate said she considered getting bellbirds re-established in Hamilton to be "stage 2" of Environment Waikato’s Halo Project, which has helped bring tui back to the city.

In Hamilton, there will be sugar-water feeders placed near the release site in the Gardens, plus two "‘acoustic anchors" that will play bellbird calls for 10 days after the release, one in Hammond Park and the other at Fitzroy Park. To monitor how many birds stay around, about 20 birds will have radio transmitters attached, with a two-week battery supply. All the released birds will carry individual coloured leg bands, and volunteers will search for them after release.

"Public reporting of bellbird sightings via EW’s Project Halo website will give an idea of their distribution throughout the city through to nesting time in the spring. This is the only long-term way for us to know how successful the reintroduction has been," Cr Southgate said.

People will be able to report sightings through the Halo website http://www.ew.govt.nz/Projects/Hamilton-Halo/Bellbirds-korimako/

or by calling EW Biodiversity Officer Ben Paris at 0800 800 401.

At this stage, an exact date for the release cannot be given. An updated media advisory will be issued as soon as more details are known. Members of the public are encouraged to attend the release whenever it occurs but should check EW’s website (www.ew.govt.nz) for the latest information.

Members of the public can keep up to date with latest news and information about Hamilton Halo at www.facebook.com/hamiltonhalo or www.twitter.com/hamiltonhalo.