Fiordland Kiwi Diaries: First “stoat-safe weight” chick

We’re on the front lines of the Save Our Iconic Kiwi initiative. Our ranger Tim Raemaekers and his team have been studying the population of kiwi at Shy Lake to find out how to best protect them from predators like stoats.

It’s been an eventful few months at Shy Lake. After Christmas we had some second-clutch nests to monitor, when the spring’s early nesters like Sinbad Colby and Filibuster will have another go. In March we also had our annual transmitter change, where we catch all our monitored adults to give them a fresh radio transmitter to allow us to monitor their breeding success the following season. That’s always a fun time, thrashing through the scrub up hill and down dale and getting up close and personal with these amazing birds.

But the key piece of work was of course to follow the survival of the kiwi chicks in the wake of the 1080 operation in winter of last year. Prior to that, we had zero kiwi chick survival across three seasons with no predator control. The operation reduced stoat numbers dramatically, but a small number of problem individuals remained and were still killing some of the chicks, while others had evaded the stoats and were growing well.

Last month we headed in as usual to check on the chicks. First up was Filibuster’s second-clutch chick. Only hatched in February, it’s the youngest chick of the season and still snack-size for a stoat. I always track in on these little chicks with butterflies in my stomach. I know that our predator control has given this chick the best chance in decades of making it to adulthood, but it’s far from a done deal as I discovered painfully earlier in the season. Chicks from Filibuster’s nests always seem to leave the nest quite young and this was no exception – at a few weeks old it was already going it alone as autumn hit the wilds of Fiordland.

With ranger Troy I follow the signal uphill through a patchwork of golden snow tussock, rocky shelves and thick monkey scrub. I zero in on a tussock on the bush edge and peer underneath tosee a little ball of soft brown feathers tucked in tight among the tussock tillers. It’s not moving and I get a sinking feeling. I reach my hand in and suddenly the feather-ball is gone and squirts out of the other side of the tussock! The chick is alive and making a bid for freedom, but size and the open terrain is on my side and in a couple of steps I can gather it up safely. What a relief to see it safe and sound. And what a spot, with a commanding view of “Lake Sweetspot” and all the way down to Breaksea Sound and the serried ranks of rugged peaks beyond. I hope the chick sticks around here!

We give the chick a quick health check: just a quick weight and bill measurement, and most importantly, a re-fit of the harness holding the tiny radio transmitter to the leg. As the chicks grow the harness will get tighter, so we need to loosen it each month. In ten minutes we’re all done and I return the chick to its cosy lair.

Next up we’re off to visit Commando’s chick. I say chick, but it’s more of a juvenile now as this one has grown strongly all the way through from hatching in October. As the chicks get bigger, they can support a more complex radio transmitter and this one has a “mortality function” – basically if the transmitter hasn’t moved for 24 hours then it beeps at a faster rate to tell us something’s wrong. As I get my first signal, it sounds normal and I can breath easy as all should be well. This is an exciting moment, as I’m expecting this bird may well have reached one kilogram, what we tend to call “stoat-safe weight”. Although it’s not a cast iron rule, generally juvies of this size and age are capable of fending off or evading a stoat, and this has been our goal for the whole project: to get as many chicks as possible to this safe weight.

We push through the wet bush until we come to an old tree base, riddled with holes. As I start looking into them, the bird boost out of the other side and is off into the bushes. Luckily for us, it doubles back and enters another nearby log. As we approach, it runs from that one too, but bails itself up against a bank and I’m able to dive and catch it. It certainly looks big and is starting to get the powerful legs and leaner build of the adults. And yes, it tips the scales at 1110 grams. It’s made it! This is such a great moment, a milestone reached after years of planning, investment and hard yards to protect our unique taonga. High fives all round.

I know that this isn’t the finish line for this chick – to help grow the population, it still needs to get to breeding age and that will take another few years in big bad Fiordland. But it should be safe from stoats now. That’s the part that we as humans are responsible for and that’s the part we can change. The rest is up to nature and other studies suggest survival from here will be high.

There’s more good news from across the valley, as rangers Monty and Bex check up on Bones’ chick which has also made it to six months old and is likely to be fine from here on in. We’ll be back each month through the winter to check up on them.

I know that we only have a handful of monitored chicks surviving, but they’re representative of dozens or even hundreds more across the larger 1080 block. And at our recent stoat survey using trail cameras, we got a bonus to support that: one of the cameras near the coast, outside of our kiwi monitoring area, picked up a chick wandering past that looked like it was from the first clutch and close to making it across the line. And of course it’s way more than were surviving previously – doing nothing is not an option, and I find it really rewarding to be a part of the solution and hopefully ensure a bright future for our tokoeka.

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This is the twenty-ninth in a series of posts about Tim’s work, follow the Conservation Blog to keep up to date on his progress.