Decoys hoped to encourage rare birds to breed in safe areas

Decoys hoped to encourage rare birds to breed in safe areas

Canterbury’s unique braided shingle riverbeds will be used for a trial to assess the effectiveness of recorded sound and decoys to encourage rare birds to breed in protected places.

Lincoln University masters student Courtney Hamblin is researching ways to improve the breeding success of tarapiroe (black-fronted tern – Chlidonias albostriatus), a tern endemic to New Zealand that breeds almost exclusively in the shingle riverbeds of the eastern coast of the South Island. Tarapiroe are classified as nationally endangered. Their current population is estimated as being between 5000 to 10,000 and is declining rapidly, largely due to the impact of introduced mammalian predators such as feral cats, stoats, rats and hedgehogs against which the terns have few natural defences.

Courtney says that while most Cantabrians probably take their braided shingle riverbeds for granted, globally they are a rare ecosystem. In New Zealand there are a number of endangered birds that have evolved to breed in the highly dynamic braided river evironment. In addition to the black-fronted tern these include kaki (black stilt – the world’s most endangered wading bird) and tarapuka (black-billed gull, the world’s most endangered gull).

Courtney says that, like the other braided river specialists, black-fronted tern require clean, weed-free shingle on which to breed.

“The problem is that while we have very large areas of braided shingle riverbeds in Canterbury, most of these areas are weed infested, and vulnerable to introduced predators and human disturbance. This directly contributes to the alarming rate at which the tarapiroe population is declining.”

Courtney plans to set up models of nesting black-fronted tern on selected islands in riverbeds in Canterbury, and enhance that with sound recordings of a nesting colony.

“What we want to see,” Courtney says, “is whether model and sound decoys will attract the terns and encourage them to nest at the selected sites. If it works, it means we could employ this technique to encourage terns to nest in areas where they are protected by weed clearance, pest control and restrictions on vehicle access, and so boost their breeding success.”

Courtney says that decoys and sound recordings have been used very successfully in New Zealand and overseas to encourage other birds to nest in safe areas, but this will be the first time it has been tried with a braided river bird.

“The major strategy for the conservation of New Zealand’s endangered species is to translocate them to suitable habitat on predator free offshore islands,” Courtney says. “But no suitable braided river habitat exists on offshore islands.

“So we have to figure out ways of making the existing environment on the mainland safer for the birds. The experience of conservation groups such as the Ashley Rakahuri Rivercare Group shows that the breeding decline of tarapiroe can be reversed if there is a concentrated effort to control predators and reduce human disturbance. But we can’t do this intensive intervention throughout all of the hundreds of kilometers of riverbed. So finding ways to encourage terns to nest in those areas that are protected could be the means through which we prevent these beautiful birds from becoming extinct.”

The use of decoys and sound recordings for black-fronted terns, a technique known as social attraction, will be trialled on eight braided rivers throughout Canterbury, including the Ashley-Rakahuri River, this breeding season, September through to January. The research has been funded by the Ashley Rakahuri Rivercare Group and the Brian Mason Scientific and Technical Trust.

ENDS

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