Kiwi Tracking Tech: The ins and outs of radio tracking 

Finding kiwi can be a real mission. But thanks to some super smart tech, tracking kiwi is now more of a science than a guessing game. In this blog post, we explore DOC’s history of radio tracking, how it all works, and how some kiwi ingenuity is changing how we monitor kiwi for the better.

Kiwi conservation is pretty wild. So wild in fact, that we’ve made a documentary mini-series about it. If you’ve been tuning into Fiordland Kiwi Diaries like me, I’m going to guess that you’ve also been struck by how expansive the landscape is. Not only is it vast, but it’s also rugged, wet and dangerous, with gnarled tree roots and densely packed ferns making the forest floor nearly impossible to move through undetected.

It’s the type of environment that kiwi thrive in – but us mere humans, not so much.  

Taking all this in from the comfort of my couch, I was left feeling a little bewildered. I mean, how do the rangers find anything in there? If your goal is to track kiwi, where do you even begin to look?  

Kiwi territories are huge, ranging anywhere from 2 to 100 hectares. 

To make it even trickier, they are always on the move, changing their burrows frequently when they aren’t nesting. If I were to put myself into the metaphorical tramping boots of a kiwi ranger, I’d have a hard time trying to locate a herd of elephants, let alone a 3kg kiwi. 

Thankfully though, kiwi rangers aren’t heading into the bush blind. They have some pretty nifty science on their side.  

This is where radio tracking enters the chat. 

So, what is radio tracking, and how will it help me find a kiwi? 

By definition, radio tracking is the practice of using receivers to gain information about animals that have radio transmitters attached to them. 

It sounds a bit complicated, but when broken down, it’s surprisingly simple.  

It all starts with a small transmitter being attached to the leg of a kiwi. The transmitter is weaved through a baby’s hospital name band and carefully secured with electrical tape – a classic example of kiwi ingenuity.  

These transmitters are designed to be strong but light, and they cause minimal discomfort to the bird.

Think of it like wearing a bracelet. 

Here’s where the magic happens. 

Powered by a tiny lithium battery and a small mercury switch, each transmitter produces a low-power radio pulse that carries a whole lot of information about the location of the kiwi.  

Now, I won’t lie to you – I’m not a physicist. So I won’t dive too deep into the physics of how radio waves work. But if you’re keen to learn more about the science behind it all, NASA does a much better job of explaining it than me. 

Each transmitter sends out a radio signal on its own unique frequency to make it easily identifiable amongst any other transmitter signals.  

To pick up the signal that the transmitter is emitting, you will need to use a telemetry set. The set consists of two pieces of very important equipment: a foldable antenna and a receiver.  

The antenna is used to gather the radio signal that is emitted by the transmitter, and the receiver converts it into audible beeps.  

To find a specific kiwi, you can tune the receiver to match their transmitters frequency – just like you would when finding a radio station. That way you’ll only hear the beeps from the kiwi you want to locate, even if there are fifty others running around. 

Magic! 

What the beep do all these beeps mean? 

While radio tracking is a science, decoding the beeps can be more of an artform. And like any artform, practice really does make perfect.  

As you saw in the video above, there is a bit of movement involved with picking up a transmitter signal. You’ll need to hold the antenna above your head and point it in each direction while listening in closely to the beeps coming from your receiver. Once you find the position where the beeps are strongest and clearest, then you’ll know your antenna is pointing towards the kiwi.

Just keep walking in the direction that the beeps are loudest, and voilà, you’ve found yourself a kiwi.

Now this all sounds easy enough in theory, and it would probably work a treat if you were standing in an open clearing. But chuck a few towering mountains in there, maybe some fast-flowing rivers, or a couple of jagged rock faces, and you’ll find the signal will bounce around and be harder to interpret.  

On top of this, kiwi move.  

You might have nailed their location, but one slight disturbance and they’ll make their escape silently through the undergrowth without you even knowing.  

This is where practice and experience come into the equation, and most rangers quickly pick up when to follow the beeps, and when they’re being misled by a cheeky mountain.  

Smart tech that keeps getting smarter 

As I said earlier, there is a small mercury switch that lives inside the transmitter, snuggled in with the battery. This switch helps us monitor kiwi movement, and in turn helps us navigate breeding season.

Picture the switch as a cylinder with a ball inside it – when the kiwi moves its leg, the ball moves too. The transmitter logs this movement as tiny electrical impulses that can be heard as beeps through your receiver. The number of beeps heard per minute will tell you how active the kiwi has been for the last 12 hours.

This means you can know when the bird has been sitting down, when it’s been moving around, and when it’s unfortunately stopped moving altogether.

Now this is where the technology gets real flashy.

In 2005, a couple of local geniuses adapted the mercury switch to record even more information about kiwi movement. We call these transmitters “smart transmitters,” and they let us know when a kiwi pair are nesting. 

Male kiwi take on the responsibility of incubating an egg, so their movement is important to know during this time – this means they get to wear the special bracelets. When they aren’t nesting, the males will be busy moving around and feeding during the night. When they are nesting, they’ll spend a lot less time moving as they focus on keeping their eggs warm, and their activity levels will drop.

This is how you know when a kiwi pair have laid an egg.

Once a male kiwi slows down his activity, the smart transmitter will start counting the days from that point. The smart transmitter will then report this information back to you through a special pulse and a series of beeps, letting you know how long the male has been incubating. From there you can estimate when the chick will hatch, and plan accordingly.

Incredible!  

How radio tracking helps kiwi conservation 

DOC has been using radio tracking for the last four decades, and it has been a real game changer for kiwi conservation.  

You probably already know that kiwi chicks are extremely vulnerable to introduced predators like stoats. In certain populations in areas without predator control, 95-100% of hatched chicks will die before breeding age.  

In areas where stoat predation is a high risk, it is vital for us to keep track of how kiwi populations are being impacted so that we can plan predator control operations. In some cases, we need to know when eggs are laid so that we can remove them from the wild to protect them – this is where smart transmitters come in real handy. 

Before DOC was using radio tracking, getting this information was an incredibly labour-intensive task.  

Rangers would tramp through the bush for hours every few weeks to find nests. Sometimes kiwi sniffing dogs were used, or rangers would perform a ‘stakeout’ and play taped kiwi calls to lure kiwi out of burrows.  

Now that transmitters are used, kiwi and their nests can be found more quickly and efficiently – sometimes from the comfort of a car parked next to a conservation area, a quick helicopter flight over a mountain pass, or a boat circling a pest-free island.

This technology allows us to gain a sneak peek into the lives of kiwi from a distance, with minimal disturbance to the animals. We’ve learnt more about kiwi behaviour, their movements, feeding patterns, and breeding cycles, all invaluable information that is vital to the species’ management and protection.

Ultimately, radio tracking means that we can monitor more kiwi, and protect even more chicks.

---

To watch the kiwi rangers in action, check out the first episode of Fiordland Kiwi Diaries below. 

---

Keen to learn even more about radio tracking? Check out our best practice guide here.