Fiordland kiwi diaries: The perils of nesting

We caught up with Tim, a ranger on the front lines of the Save Our Iconic Kiwi initiative. This is the fourth in a series following the work he’s doing to save the Fiordland tokoeka (kiwi). You can find the first post here.

The wintery scene in Fiordland. Photo: Tim/DOC

With a roof over our heads and a track to help us get around without pushing through snow-laden bush for hours, we were ready to start monitoring kiwi nests.  And not a moment too soon, as early July saw the first pairs starting to nest.

Photo: Tim/DOC

The adult kiwi carry “smart” transmitters developed by Wildtech Ltd. Each transmitter has a motion sensor inside it that records whether the bird is moving or not. If it jiggles enough to pass a certain threshold, the bird is considered “active” and the transmitter logs this information 24/7. The idea is that when a bird starts incubating an egg, its activity levels will drop as it spends less time foraging and more time sitting. This method is widely used on kiwi projects across the country.

The transmitter then spits out a code of beeps that we can pick up on our radio receivers and carefully count, to find out how many hours the bird has been active on each of the last 14 days. We do this for all 23 birds at the start of each trip, adding up to about 4000 beeps counted. It’s a chilly job at this time of year, and a poorly timed gust of wind can be enough to miss some crucial data and have to wait 10 minutes for the code to play again. But it’s well worth it, as when we graph the data we can see a pronounced drop in the activity of several birds.

Bex, Jenny and pilot Gav fly out over Lake Manapouri. Photo: Tim/DOC

On a crisp sunny day, Em and I set out to track down the nest of Filibuster and his mate Fortuna. The snow squeaks under our feet, icicles sparkle in the sunshine and under a dripping bluff, we find shrubs perfectly encased in crystal clear ice.  Magical.

Tim tracking kiwi at Shy Lake. Photo: Em Oyston

Following the transmitter signal from different directions, trying to keep each other in sight, we advance gingerly through the thick scrub on the side of a small bluff. A tell-tale hole in a rock alcove reveals, on closer inspection, a glimpse of the feathers on Filibuster’s back. We think that males incubate during the day and females at night. But that’s just a guess based on the behaviour of northern Fiordland and Haast tokoeka – nobody has studied the nesting habits of southern Fiordland tokoeka before. We set up a trail-cam, a small camera triggered by motion sensors, and retreat.

Em on the way home from Filibuster’s nest. Photo: Tim/DOC

Two weeks later, Bex revisits the nest to change the memory card and batteries. Filibuster is still on there which is a good sign. Back at base, we have a look at the footage and are delighted to see some clear images of Filibuster and Fortuna coming and going, and pulling leaf litter inside the burrow to line the nest. They’re easily told apart by the Fortuna’s longer bill (standard in females) and the transmitters on different legs.

But as we flick through the photos, disaster! Looking out of the nest hole in broad daylight, bold as brass, is a stoat. We know there are plenty around, but it’s still a shock to see it. It spends about ten minutes digging up the nest litter, only its tail visible to the camera. As far as we can tell from the trail cam footage that morning and night, no birds are present at the time of the visit, which could be a bad sign in itself. The camera shows them returning to the nest for the next fortnight though, so there is hope. At this stage, the best hope may be that Fortuna had not actually laid yet and the pair were just getting themselves into breeding mode by preparing this burrow for weeks. We’ll be checking the burrow for an egg on the next trip. Unfortunately, it doesn’t look good for a little FiFo chick this year. But I suppose that’s why we’re here.

Stoat caught on camera at Filibuster and Fortuna nest

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