Back from the brink: part two

How an obsession with killing things is saving New Zealand’s wildlife (7 minute read)

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In the tree above me is a small bird, singing a song that seems disproportionately loud for its size. I’m looking up, and occasionally I see him hopping from branch to branch, a silhouette against the sky. I stand and listen for some time, knowing that I’m hearing something special.

The bird is a North Island robin, a grey bird with the endearing habit of checking out humans that enter its territory. Robins sometimes come quite close – I’ve already had one within a couple of metres of me. The species isn’t particularly rare, but it is much less common than it used to be, and in decline. Today, though, the robin singing above me is the third I’ve seen in the last half hour.

North Island robin (photo credit: Imogen Warren).

Here at Zealandia sanctuary, the species is thriving.

If it weren’t for Zealandia’s fence, there wouldn’t be any robins in this area at all. Zealandia is tucked between the suburbs of Northland and Karori, just minutes from central Wellington, and robins are not city birds. Mostly, the North Island robin is found in large areas of forest in the central North Island, or on offshore islands. Zealandia’s birds are the descendants of birds brought over from Kāpiti Island and released into the predator free sanctuary in 2001 and 2002.

When I think about the impact Zealandia and its fence has had on Wellington, the robin gives a great illustration. In typical mainland sites without predator control, robins are spread out widely, occupying territories of 1-5 hectares. Mainland robin populations also have almost twice as many males as females, because the females are more vulnerable to predators. In Zealandia though, the robins reach much higher densities, even though they don’t quite reach the levels seen on offshore islands where the robins can’t disperse. Zealandia’s robins also have similar numbers of males and females.

The success of the robins at Zealandia isn’t obvious just to scientists. Visitors to the sanctuary are likely to meet them, because robins are fearless around humans. It isn’t only robins that are easy to see and hear either. On my walk around Zealandia last weekend, I also spotted tīeke, whitehead (pōpokatea), kākā, korimako (bellbird) and tūī. The forest was alive with birdsong, much more so than the forest on Tarikākā where I usually walk, even though there’s a predator control programme there. Seeing and hearing rare birds thriving in a predator-free sanctuary gives a powerful message about what New Zealand lost when rats, cats, possums and mustelids were introduced to New Zealand. Equally powerful is the message about what can be gained. For some of New Zealand’s birds it is too late, but Zealandia shows that species can be brought back from the brink, and not just on offshore islands, but in the middle of a city.

North Island kākā (photo credit: Imogen Warren).

But bringing the birds back to Wellington has involves more than just Zealandia. Wellington’s councils have also turned their attention to predator control, as part of a programme to protect what they call “key native ecosystems”. These are areas that are important for native plants and animals within the Wellington region, and they include a number of areas close to Wellington City. To protect these areas, local councils have ambitious biosecurity programmes, controlling introduced mammals such as goats, rabbits, rats, stoats and possums, as well as weeds. Within the Wellington City Council area, more than 5700 hectares are covered.

Without this biosecurity programme, many of the birds that stray beyond Zealandia’s fence would immediately fall prey to the predators outside. But, thanks to predator control, kākā have returned to Tarikākā and tītipounamu (riflemen) are breeding on Te Ahumairangi Hill, less than a kilometre from Wellington’s central business district. Even the tīeke, one of the bird species most sensitive to predation, is breeding outside Zealandia’s fence. Many Wellingtonians don’t realise that some of the credit for the “halo effect” of abundant birdlife surrounding Zealandia belongs to the council’s biosecurity programme. However, an increasing number are not just aware of the council’s work, they are getting involved themselves.

Although the council programmes cover a large part of Wellington, they can’t do everything. That’s where local communities come in. Wellington City Council works with nearly 30 groups of volunteers who are trapping predators in their local area, as well as supporting the  “Predator Free Wellington” initiative. One of these groups is in my neighbourhood – “Predator Free Khandallah”.

I saw an example of their work recently when I was walking my dog Donna. As I mentioned last week, Donna sniffed out a trap tunnel beside the track where I walk her every morning. I was curious about the trap, so I looked up Predator Free Khandallah on Facebook, posted a message, and a day later I was talking to one of the volunteer predator trappers, local resident Briony Ellis.

Although we live in the same suburb, we meet over video call since that’s easiest to arrange around work. Ellis tells me that she’s the one who coordinates Khandallah’s reserve trapping programme. Most of the traps are in Khandallah Park, on the slopes of Tarikākā, which is the best and largest area of bush. Ellis and two local volunteers manage more than forty traps up there. Two other volunteers help Ellis maintain the traps in the smaller parks. In total, there are 78 reserve traps and so far these have caught just over 300 predators, mostly rats but also stoats and hedgehogs. But they’re not the only ones maintaining traps in Khandallah. Ellis is part of the team that coordinates a backyard trapping programme, taking a particular interest in the trapping that happens in backyards on the edges of reserves. There are several hundred backyard traps around Khandallah, and those traps have caught more than 4700 predators.

Maintaining several dozen traps in at least five reserves is a lot of work, and I ask Ellis what motivated her to become involved in predator control. She credits Zealandia and Wellington’s recovering bird population for her interest in controlling predators, but it’s not a rare bird that she gives as an example. Instead, she talks about seeing tūī in Bowen Street twelve years ago. That’s right in the heart of Wellington, near Parliament, and Ellis tells me she was “blown away”. I understand what she means about the tūī. Since I’ve been living in Wellington, they seem to have become increasingly common. I hear them when I’m walking on Tarikākā. I hear them when I’m standing at the bus stop. I hear them when I’m working in my garden.

Our observations of tūī numbers are backed up by council monitoring data. Every year, Wellington City Council does a bird survey across the city. The surveys are done at 100 different sites using “5 minute bird counts”, that is, staying still for 5 minutes and recording every bird seen and heard. Since 2011, when the counts started, tūī numbers have increased steadily, and they are now recorded in most of the counts.

The council’s bird monitoring shows other good news as well. Kererū (native pigeon), kākā and kākāriki (red-crowned parakeet) are also increasing steadily in Wellington City, well outside Zealandia’s fence. Neither the kākā nor the kākāriki would be in Wellington without Zealandia, but the growing numbers in reserves such as Khandallah Park is due to the efforts of Wellington’s councils and the army of volunteer predator controllers around the city.

Ellis talks about the abundant birdlife as the “reward” for predator control, and I think that’s a great way to look at it. Killing animals isn’t something that conservationists do lightly. And yet, around Wellington, that is what many of them are doing, because they know that it’s making a difference. Their efforts have brought an abundance of birds back to the city.

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