In a bush reserve near Zealandia in Wellington, a murder mystery is unfolding. Allison Hess investigates.

On a summer walk through one of the capital’s most popular bush-clad reserves, you wouldn’t expect to find a body strewn limp and cold across the leaf-littered trail. But volunteers staking out the Waimapihi Reserve (formerly Polhill) every week have grimly come to expect it.

A sinister pattern starts in late summer. Toutouwai (North Island robin) spill over from fenced eco-sanctuary Zealandia Te Māra a Tāne, looking for new homes and a mate. They are soft grey birds with long toothpicks for legs and are only found in Aotearoa. They are known for their bold and curious nature in the forest, hopping close to trampers and even jumping onto shoes to get a better look at you.

And for a while, it’s great. 

But like clockwork, one by one, the toutouwai disappear. 

Some are never seen again, while others are discovered lifeless by reserve visitors. By spring, only a few pairs remain to nest. By early summer, most of them (particularly the mothers and babies) are gone, too.

The Ngā Kaimanaaki o te Waimapihi community group has been doing its best to lay down the welcome mat for species jumping the predator exclusion fence: thousands of trees planted, invasive weeds removed, an intensive predator trapping network and a staunch stance on dogs on leads. Sick to their stomach at the thought their reserve was becoming a robin graveyard, group members called for help in late 2022.

Enter Dr Rachael Shaw from Te Herenga – Victoria University of Wellington, who is investigating the unsettling pattern of disappearances. The senior lecturer in behavioural ecology enlisted the help of her students and bird nerd volunteers Rachel Woolford, Annette Harvey and Melissa Boardman.

They stake out the reserve most weekends, armed with binoculars and long-lens cameras. Walking with Rachel Woolford along a leafy track, she lights up as she describes the lives of the toutouwai they have been watching for the past year.

“A Zealandia-banded male claimed some territory near the Hoki Mai track and found himself a lady-friend in spring. They courted, which is basically the male doing a lot of singing and bringing food gifts to a female. The female began to build a nest in early October, with the male again dutifully bringing her food while she incubated their eggs. The nest was too high to put cameras on, but we kept tabs on the family,” Woolford says.

So sweet. 

Then, things turn dark.

“In November, the same weekend they were due to fledge, the mum toutouwai and all the chicks vanished. The dad continued to bring food and call out for his family for days before eventually giving up. His whole family was wiped out. He’s alone now, but we still see him around his territory.” 

They try not to get too attached, but it’s hard not to be heartbroken after each disappearance or death, Woolford says. You get to know the individual robins. Banded in Zealandia or by qualified bander Harvey in the reserve, they are easily identifiable from their coloured bracelets and given nicknames.

Toutouwai are fiercely territorial, especially the males. They will stick to the same patch of forest for their whole lives and spend a lot of time on the forest floor or in the lower canopy, where they hunt for bugs and make their nests.

The volunteers recorded at least 49 individual birds in Waimapihi during 2023, but by spring, only a handful remained, and only three pairs nested in the reserve this season. 

“Groucho (banded green/orange) is a single dad who would not give up on his babies even when the mum disappeared, and wet, windy weather caused his nest to collapse to the ground. Only one chick survived the fall and holed up in the middle of a gorse bush, but Groucho continued to feed it all through bad weather.”

Since then, Groucho has been found dead, and his chick has not been seen for weeks. 

What is happening to these poor birds?

Introduced predators are the likely suspects. 

Rats, weasels and stoats are all possible suspects; however an intensive bait and trapping network has lowered numbers to the point that tracking tunnel indices show basically no mustelids and few rats.

Instead, many clues lead to another sharp-clawed predator that roams unhindered in the reserve: cats.

Dr Shaw reveals the evidence gathered so far: a gut-wrenching trail camera video of a cat preying on a toutouwai nest, cats regularly appearing on trail cameras, and an autopsy confirming a cat-depredated toutouwai carcass. “We are gathering more and more evidence that predation, particularly by cats, is a big issue for birds in Waimapihi.

“Almost every bird we have seen in Waimapihi this past year has been a first-year juvenile. By contrast, in the Zealandia study area, we have some birds who have lived for more than 12 years and successfully nested every single season,” Shaw says.

She’s not the only one who has suspicions about feline involvement: a 2016 study into the activity of domestic or pet cats inside Waimaphihi Reserve revealed multiple cats triggered nearly every camera in the reserve on 31 out of 32 days.

Back then, the attitudes of nearby cat owners trended towards apathy: the above study found that 72% of cat owners thought cats posed a threat to native wildlife in urban reserves. But, only 39% of them thought cat-free zones were a good solution to the issue of cat predation.

There’s plenty cat owners can (and already) do to keep their beloved moggies and wildlife safe and happy. Cat owners are an essential part of the solution, and there’s an SPCA-promoted consensus that keeping cats at home or contained on property is better for their welfare.

Shaw believes the community-led monitoring project will provide valuable data demonstrating how much vulnerable species struggle to survive in urban reserves. 

“We want to ensure that we document what is happening, both to help push for change in how we think about pet cats and to have a baseline for what is currently happening in Waimapihi. Hopefully, once we have better ways of managing the threat of cats, we will see drastic improvements in survival and nesting success for toutouwai.

It’s not all about toutouwai, either. Shaw calls them the “proverbial canary in the coalmine” due to their bold and ground-foraging behaviour. If the reserve can become a safe place for them, it will likely become safe for other vulnerable species, too.

This mystery is quickly reaching its conclusion, evolving beyond “whodunnit” to the pressing question of “who will take action?”

The fate of the Waimapihi toutouwai hangs in the balance. We risk becoming unwitting accomplices in a grim situation if we do not act.