Rare braided river birds in Hurunui protected for another season

Braided rivers are rare ecosystems. The plants and animals that live on them are highly adapted to living in the rivers’ dynamic physical environment.

“In New Zealand, our braided rivers support high levels of endemic, threatened, or at-risk species,” said James Schaap, Land Management and Biodiversity Advisor. “Many of these species are either unique to the braided river environment or dependent on it to complete a critical life phase. Canterbury has two-thirds of New Zealand’s braided rivers.”

In 2017, the Hurunui Waiau Uwha Water Zone Committee hosted a meeting of braided river experts to identify the key values, threats, and gaps for braided river biodiversity management in their region. Together, they agreed that a strategic management approach to address the multitude of threats facing our braided river ecosystems was urgently needed.

This group formed the Hurunui Biodiversity Trust which now works to protect the rare species living on the Hurunui and Waiau rivers in partnership with the Department of Conservation (DOC), community groups and landowners.

Braid islands provide the best breeding habitat for many species of braided river birds.

The Braided River Birds Flagship Programme, with the help of DOC, has focused on habitat enhancement, trapping predators and monitoring efforts.

Some of the ongoing work to improve habitats:

• Deepening channels around breeding islands to create a ‘moat effect’, discouraging predators from reaching the islands.
• Adding and shifting gravel to the top of islands to add height. This protects the islands from flooding which can sweep away nests.
• Predator trapping to lessen the number of raided nests.

Monitoring of breeding sites

The group has also conducted ongoing monitoring of breeding success rates both on and off the managed islands to identify the best interventions for future efforts.

The results on the Waiau River speak for themselves. In the last season, black-fronted tern achieved 96% hatching success of one or more chicks on the protected Shark’s Tooth Island. This compared to 64% on the natural islands that the group monitored and only 9% on the mainland.

“This is really impressive in a challenging environment, it proves the efficacy of the interventions we have undertaken and it makes a good case for further investment,” said James.

Unfortunately, at the enhanced island on the Hurunui, NIWA Island, no black-fronted tern colony was established this season. This was most likely due to disturbance from other river users such as clay pigeon shooting. Happily, banded dotterels did successfully breed on the island. Breeding activity has been recorded for all past seasons of the project at NIWA Island.

Predator trapping resulted in a total of 175 target species caught at NIWA Island and 73 caught at Shark’s Tooth Island.