Between February and August this year, 34 juvenile tūturuatu were introduced to pest-free Mana Island. The birds were raised as part of a captive breeding programme by the Isaac Conservation and Wildlife Trust and Pūkaha National Wildlife Centre.
After their initial release the tūturuatu dispersed to the mainland, where they often fall prey to introduced predators like cats, rats and stoats. When some of the birds showed up at Plimmerton and Waikanae they were recaptured and returned to Mana Island along with three more tūturuatu from the Isaac Conservation and Wildlife Trust. Radio transmitters were attached to learn more about the birds' behaviour.
Now, no tūturuatu remain on the island.
Two birds form the last remnants of the Mana population. It is now known some of their less fortunate compatriots were on the menu for a kārearea/New Zealand falcon that appears to have taken up residence on Mana. Kārearea is a native species that is itself coming back from the brink and repopulating areas where they were once common.
The small tūturuatu are easy prey for the fast kārearea, as a volunteer on Mana Island discovered soon after releasing the last three tūturuatu in late August. She witnessed the falcon swoop in and chase one of the birds in flight and, by following radio transmitter signals, was able to confirm its fate. Unfortunately a second bird fell prey to the kārearea the following day.
A decision was made to evacuate the third tūturuatu, which has been taken to Pūkaha National Wildlife Centre where it can contribute to the national captive breeding programme. The second known surviving tūturuatu has been spotted on the mainland, and attempts are being made to recapture it to join its fellow survivor.
"This situation highlights some of the complexities that come with managing a critically threatened species, especially one with such a small overall population and particular habitat needs," says Dave Houston, leader of the Tūturuatu Recovery Group.
The wandering habits of these small wading birds are well-known, he says, and Wellington birders have enjoyed sightings of this rare bird after previous releases. But it was highly unusual for an entire cohort to leave the island within a few months of release and it was thought that something might be driving the birds from the island.
"Kārearea would likely be natural predators for tūturuatu, and it is a success story to have one on Mana – but it poses a complication when trying to establish a new tūturuatu. It's unfortunate to have lost these birds, and we know this sentiment is shared by those in the local community who have been so engaged with the release of these quirky and endearing little birds.
"However, we have learned a lot to inform future conservation strategies with tūturuatu.
"The species' recovery depends on establishing new populations to build on the 243 adult birds in the wild. Pest-free islands are our best option at the moment but the two main current strongholds for tūturuatu – Rangatira and Waikawa islands – are reaching population capacity. It was worth exploring Mana Island as a possibility."
The Tūturuatu Recovery Group will continue to explore locations to establish a new population.
