DOC rangers in Twizel were alarmed when a concerned citizen alerted them to mallard ducks preying on pūteketeke chicks in the Mackenzie Basin, recently.
Rangers were shocked when a person sent in photos of three ducks hunting and killing freshly hatched native pūteketeke (Australasian crested grebe) chicks next to Lake Alexandrina, just south of Lake Takapō/Tekapo.
The pūteketeke hit global headlines when comedian John Oliver successfully campaigned for the Australasian crested grebe to win the Forest & Bird, Bird of the Century crown in 2023.
DOC Principal Biodiversity ranger Dean Nelson says they were horrified to see graphic photos of pūteketeke chicks being eaten alive, knowing how unusual it is for ducks to prey on other birds.
"Mallard ducks usually eat plant material, with a little bit of protein from insects and snails during the breeding season. It was shocking to see them eating pūteketeke chicks. We went out there straight away and I observed three mallard ducks in the outlet creek where the grebe nests are. They were actively scoping out the pūteketeke nests to see if they had chicks.
"The adult pūteketeke didn't see the danger as they don't perceive the ducks as a threat."
This duck behaviour was unknown to DOC experts, and there was a concern that it would spread, as ducks learnt from each other, says Dean Nelson.
"There was a case which was referenced in a research paper from a Cambridge University scientist describing how a group of mallard ducks were attacking and eating the chicks of two common bird species in Romania in 2017. It claimed this was a world first and the ducks may have been searching for a source of protein before laying eggs and nesting."
Dean Nelson says the member of the public did exactly the right thing in calling DOC about the incident and taking photos as evidence, otherwise he says it would've been hard to believe.
"This is a great example of people taking action for nature and looking out for our vulnerable species. While some people think the pūteketeke is introduced because of its name (the Australasian crested grebe), the reality is they're native and are classed as nationally vulnerable.
"We want the public to be really engaged with nature. People can be our eyes and ears out 'naturing' and that's fantastic for us, as our rangers can't be everywhere," he says.
Last December campers and boaties around the popular Lake Benmore shoreline in Canterbury were asked to look out for pūteketeke over the summer holidays after reports of nests being disturbed at the Ōhau C campground. Many nests were adjacent to the boat ramp and spread out around the lakeshore.
The pūteketeke colony has had 40 to 50 nests each year for the last five breeding seasons and birds have raised their young much later than usual in the outlet creek next to Lake Alexandrina. The 'colonial' style of nesting so close together makes them easy prey for predators.
DOC staff have caught the three offending ducks with nets and removed them from the site and humanely euthanised them. They are also heading out again today to check that no other mallard ducks have learnt the behaviour.
Anyone who sees sick, injured or at-risk native wildlife can ring 0800 DOC HOT (0800 362 468).
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Pūteketeke were once found throughout New Zealand but now they're only found in the South Island living on lakes. At least 100 South Island lakes once had grebes but there has been a decline in Marlborough, the West Coast and Fiordland. Only Canterbury and Otago remain as strongholds. Predators include stoats, ferrets, cats, and raptors.
