Source: NZ Department of Conservation
Date: 05 December 2025
In December 2024 the feral tom cat reached a large island in the river where the endangered terns were nesting. It killed and ate several adult birds, chicks and eggs, disturbing the colony and causing almost all 95 nests to be abandoned.
Last week contractors, husband and wife team Jasen and Shannon Mears of J & S Mears, were carrying out a leg-hold trapping operation, targeting feral cats to protect nesting tarapirohe from predators. They caught 11 feral cats, including the 6-kg individual responsible for last year’s colony attack. But it wasn’t easy.
Shannon Mears says they tracked the large feral tom cat – identified by its long stride and distinctive prints – for three days, before finally luring and trapping it.
“It took three nights to catch it. Each morning, we would find the cat had yet again evaded or ignored traps and bait. Its prints clearly showed him visiting the river near the same tern colony he decimated last year to check the water level. It would have only been a matter of time before the river level dropped, and he would have been able to reach the colony again.
“We went to great lengths to lure it with whole rabbits as decoys, wing traps and buried leg-hold traps covered by tissue paper and soil, in which it was eventually caught.
“Even then it managed to pull the stake out and hide in a den about 200 metres away in the middle of the Acheron campsite, where our dog, Billy, tracked him.”
Shannon says it was challenging to outsmart the wily and trap-shy cat which had carefully avoided the many leg-hold traps set around the colony and network of over 700 kill traps in the wider area.
“It was a relief to finally catch it and a win for the black-fronted terns, which will be a lot safer this breeding season,” says Shannon.
DOC South Marlborough Principal Ranger Pat Crowe says after the devastating loss of the colony last year, it’s good news to see the results of the massive trapping effort.
“It was sad to see the impact a single cat had on an entire colony of these special birds when everyone was working so hard to protect them. So, it’s gratifying it has now been removed along with ten other feral cats.
“Controlling predators like feral cats, ferrets and stoats is difficult work, especially when you’re dealing with trap-shy individuals but it’s critical to give species like tarapirohe and other braided river birds a fighting chance.”
Pat says apart from a flooding event in late October which disrupted early nesting, it’s been a successful breeding season with no signs of predation by introduced predators within the trapping area.
The Waiau Toa/Clarence River is important habitat for black-fronted terns. There are at least 12 colonies nesting on islands in the braided river this year and 206 nests have been recorded in the six monitored colonies.
People can do their bit to help protect the tern colonies when they’re out naturing in the Molesworth Recreation Reserve by giving the birds space and keeping out of the nesting colonies, says Pat.
If you spot a feral cat while out driving or walking in this area, please contact the DOC Renwick office: renwick@doc.govt.nz
Predator control, island enhancement for nesting, and bird monitoring has been undertaken in the area for about a decade. This project is supported by Ngāti Kurī. It’s funded by Canterbury Regional Council (Environment Canterbury), DOC and Toitū Te Whenua Land Information New Zealand (LINZ), and much of the work is carried out by J & S Mears Contracting and Wildlife Management International Limited which monitors the birds.
Background information
Black-fronted terns are endemic and have a conservation status of ‘Threatened – Nationally Endangered’. They have a national population of 5-10,000 birds, which is declining.
Feral cats are opportunistic and skilled hunters, and among the top introduced predators across many New Zealand’s ecosystems. With their high prey drive, they have a major impact on native birds, bats and lizards.
Braided rivers like the Waiau Toa are dynamic and globally rare ecosystems which face pressures from weed encroachment, introduced predators and land use changes, in addition to human disturbance.
Contact
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Email: media@doc.govt.nz
