Predator protection boosts black-fronted tern breeding

Black-fronted tern breeding in Molesworth Station has taken a turn for the better with terns in protected colonies having their most productive breeding season in five years.

In the 2016-2017 breeding season, nesting productivity was five times higher at the protected colonies than at colonies with no protection measures.

Terns in the protected colonies had an average productivity of 1 chick per nest (147 chicks and 152 nests) compared with an average productivity of 0.2 chicks per nest at the unprotected colonies (55 chicks and 348 nests).

Black fronted tern/tarapiroe has a threat status of nationally endangered and its numbers are declining. Tern colonies in the upper Clarence and Acheron rivers are being monitored in a five-year project that is testing a new conservation management regime aimed at improving their breeding success.

Department of Conservation South Marlborough Operations Manager Phil Bradfield said the significantly improved breeding success was a highly encouraging indication the conservation measures were working.

“Black-fronted terns had low breeding success in three years of monitoring before protection measures were put in. The average productivity in each of those years was only 0.18, 0.08 and 0.10 chicks per nest which gave us cause for grave concern.

“The most recent breeding season was the first in which a full predator trapping network was in place at three colonies along with habitat enhancements to river island breeding sites.

“We caught 281 predators in our trapping network around the three protected colonies over the breeding season, including hedgehogs, stoats, ferrets, weasels and wild cats. We’re pleased that the traps and habitat improvements appear to be helping to keep the black-fronted terns safe from predators with more chicks surviving.”

Tern breeding success will continue to be monitored for another three years to test how well the protection measures are working and to assess what adaptions or further measures might be beneficial.

The habitat improvements included broom and other woody weeds being cleared from terns’ river island breeding sites to provide more gravel nesting habitat.

Water channels around islands were widened and deepened using a bulldozer and the excavated material was used to increase the height of islands above the water channels. The measures make it more difficult for predators to access the islands and provide some protection from flooding.

The black-fronted tern project is being carried out by Wildlife Management International working with DOC. It is jointly funded by the Environment Canterbury Braided River Regional Initiative, the Kaikoura Water Zone Committee’s Immediate Steps Funding and DOC.

Control of broom, gorse and willows along the upper Clarence River, funded by Environment Canterbury, Land Information New Zealand, Landcorp and DOC, has also provided more breeding habitat for black-fronted terns.

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