The hidden risk for the world’s smartest bird

It’s Mount Cook in winter and a kea is standing on the hut roof. It’s working out just the right time to flick snow onto the heads of the poor people walking below.

This sums up the kea, the bird that New Zealanders made a roadside gymnasium for, in an attempt to distract the cheeky birds from shifting road cones into the middle of the Homer Tunnel. 

Kea love tinkering. They often turn on taps, and a kea once managed to lock a mountaineer in the toilet at the Mueller hut.

Conservation devices used in kea habitat have to be ‘kea proof’. We have to use extra-long screws to secure the stoat traps, so that kea can’t prise them open and end up tangled in the devices. 

But unfortunately, sometimes the kea’s curiosity and intelligence work against the bird.

This iconic Nationally Endangered species is endemic to the South Island and taonga to Ngāi Tahu. Yet they’re in serious trouble across half of the species range and we don’t have the benefit of time to save them.

There are now huge gaps where kea used to be present. It’s estimated there are only about 3000-7000 kea left, and in areas without predator control they are still declining. 

For some context, there are 68,000 kiwi left. 

So what’s the problem? Well, kea are ground-dwelling birds, making them incredibly vulnerable to predators. The ‘public enemy number one’ for kea is considered to be stoats; that clever, voracious hunter that can live in any habitat, swim, climb, and hunt at day or night.

But new research shows a new enemy has emerged. 

A kea was once spotted having a tug-of-war with a feral cat over a rabbit carcass. In that particular moment, the kea was holding its own. Sadly, it appears since then the feral cats are winning out.

Feral cats are killing kea, in numbers comparable to stoats in eastern parts of the South Island. 

Since 2019, a five-year study has followed the progress of 45 radio-tagged kea in areas east of the Southern Alps/Kā Tiritiri o te Moana between Lewis and Arthur’s passes, mostly in valleys where there is no predator control.

Researchers want to learn what is driving the decline of the birds east of the main divide. Thanks to this study, we are learning more about the dangers of feral cats.

So far, 13 of those 45 kea have been killed by predators. The cause of death has been about evenly split between feral cats and stoats.

To figure out the cause of death, the field team sends the kea corpse away for forensic analysis. They also use field signs to determine the likely predator, using techniques you’d typically see on police shows on TV. This may seem like overkill to some, but kea really matter.

Let me explain. When a cat kills a larger bird like a kea, it’s a mess. There will be feathers everywhere. The corpse might be discarded in a prominent place above ground. Cats have stronger jaws than stoats and will easily chew through a kea’s leg bones, so the metal leg bands that a kea wears slide off and are often left lying beside the corpse.

A stoat’s kill is quite different. They often decapitate their prey, and then eat the muscle and tissue. Then, like a squirrel, they store what’s left in different caches underground for later.

Keas are sturdy but they’re not fighters. They don’t use their beak – they freeze and rely on camouflage. That said, they’re physically more of a challenge than, say, a rock wren.

The thing is, if feral cats are killing kea, imagine how hard it is for our other smaller species. 

We already know that kiwi, whio, weka and rock wren are either sparse or gone from many South Island eastern habitats, and that’s largely due to introduced predators.

The problem with feral cats

Of course, it’s not news that feral cats kill native species. Kākāpō had to be removed from Rakiura/Stewart Island after feral cats brought their numbers down to 60. A single feral cat in Ohakune killed 102 short-tailed bats in seven days. Threatened reptile populations like Grand and Otago skinks are critically low due to depredation by feral cats, and research is currently looking into the damage they inflict on the whio/blue duck population.

We know it’s really hard to place blame on specific predators for the decline of a species. 

But, as a country we appear to have a blind spot when it comes to feral cats. These incredible hunters live right across New Zealand, from sea level to 3000 metres up. They are extraordinary predators that have huge home ranges. One feral tomcat on the Auckland Islands was recently tracked hunting over a 60 square kilometre area – that’s four times the size of Auckland Airport.

Even if they’re well-fed, a cat’s prey drive means they love to hunt and they’re built for it. They can see in a sixth of the light needed by humans, and hear the ultrasonic calls of rodents.

If you’re picturing feral cats living their best lives out in the wild, I’m afraid that’s not the case. Feral cats have tough, short lives. They’re often starving and diseased. The females are pregnant repeatedly from a young age and sometimes unable to look after their litters.

So what’s being done about feral cats?

We’ve known that feral cats are a problem for many native species for a while now, and the Department of Conservation (DOC) has a mandate and best practice to manage them on public conservation land where it can.

That doesn’t make it an easy job, though. Feral cat control is expensive, labour-intensive, and much more difficult in areas where kea are present because they can get caught in the traps too.

Another problem is that we don’t really know how many feral cats there are in New Zealand. We do know their preferred food source is rabbits when they are present, so where you find rabbits, you are more likely to find higher numbers of feral cats. It looks like this is why we have a problem east of the main divide – where farmlands and drylands (typical rabbit habitat) border kea habitat.

While we haven’t solved the feral cat problem yet, there are some good precedents to take heart from. It took until the mid-1990s to find out that stoats were killing kiwi chicks at a rate that was rapidly leading to the decline of the species. Today, we’re very good at stoat control. Once we understand a predator, we can deal with it.

Thanks to this study, we’re getting new data demonstrating the extent of the feral cat problem for kea in the east.

We’re also developing new tools for more efficient control of stoats and feral cats. DOC is leading the development of baits for use with the toxin PAPP (para-aminopropiophenone). In Australia they use a similar carnivore bait for cats and foxes. This work is still in the early stages though, and we still need to be confident that it’s safe for native birds.

To help us manage kea as well as possible, we need to understand everything we can about the species’ behaviour, preferred habitats, and population dynamics both now and in the past. We’re currently working with iwi to figure out where the gaps in our knowledge are, and we’re drawing from mātauranga Māori as well as western science for this.

What can we do?

If you see a banded kea, let us know. The kea sighting database set up by the Kea Conservation Trust has been hugely successful for keeping tabs on birds. Over 10,000 sightings have been recorded by the public, meaning we’ve got great data on kea movement. This can inform how we manage them. Recently, a hunter in Whataroa on the West Coast sent in a photo of one of the 45 study kea from the Eastern South Island project. Romano the study kea had just decided to fly 96 kilometres from home.

Love this bird, but from a distance and please don’t feed them. Our obsession to get a wildlife selfie for the gram isn’t as harmless as it may seem in the moment. Experiences with weird urban food make kea more likely to try other strange things – plastic, lead-head nails, or 1080 pellets to devastating effect.

Oh, and do what you can to control your own domestic cat. There is absolutely a place for domestic cats in New Zealand, but our feral cat problem is fuelled when people don’t look after their pet properly. 

If you don’t get it desexed and microchipped, you can end up with unwanted kittens. Some unscrupulous owners dump these kittens in the wild, and if they survive, they may eventually become feral and top up the population.  

A cat that was found with 17 native skinks in its stomach was black and white – that’s not a colour combination that lasts well in the wild on the New Zealand mainland. The ranger who found it thought it was likely to have been a recent descendent of a wandering domestic cat from nearby.

The good news is that kea can be very productive in the absence of predators. They breed most years, and successful breeders fledge between one and four chicks each season. That’s the kind of population growth we need for this long-lived and slowly reproducing bird. If we can get predator numbers low enough so that they can breed successfully, this species can bounce back. We have a long way to go and need everyone to pull together to give the smartest bird in the world a fighting chance.