Counting rimu fruit on kākāpō islands

Department of Conservation —  16/03/2018 — 1 Comment

By Bronnie Jeynes, Ranger

Kākāpō are one of New Zealand’s unique endemic species. These huge, endangered, flightless and nocturnal parrots only breed during years when the rimu tree masts (every few years).

With only 149 individuals left and only surviving on three, predator-free offshore islands, kākāpō breeding seasons are highly anticipated by the dedicated Kākāpō Recovery Team who work to save this species.

Kuia on her nest during 2016. 📷: Theo Thompson.

Kuia on her nest during 2016. 📷: Theo Thompson

Team Technical Advisor Daryl Eason keeps a close eye on the average seasonal temperatures, comparing one summer to another. He’s watching for the patterns that will indicate that we have a potential mast, or mass fruiting, for the rimu trees on Whenua Hou and Anchor Island. Rimu follows a complex four-year pattern. If the summer of year 1 is warmer than average, followed by a cooler than average summer in year 2, then the rimu will produce pollen during the summer of year 3 and finally fruit during the summer of year 4.

The weather patterns are looking good for a potential mast during 2019. Rimu trees on the mainland had high amounts of pollen on them over the summer, and so the whole team has high hopes as ranger Theo Thompson, accompanied by Jono Moore head out to Whenua Hou and Anchor islands to count the green rimu fruit developing on the trees there.

Using ropes, Theo and Jono scale the chosen sample rimu trees on Whenua Hou and Anchor, counting how many tips on certain branches are upturned and hold the tiny beginnings of small green fruit at their tips.

On Whenua Hou the number of fruiting tips varies between branches and between trees, but it is obvious that there is fruit forming, and lots of it.The final total shows that 47% of tips are carrying fruit. This is 10% higher than any results we’ve previously seen for Whenua Hou!

Results from the annual autumn counts on Whenua Hou.

Results from the annual autumn counts on Whenua Hou

On Anchor, the results aren’t as consistent and it’s hard to predict what the average will be. Some trees have very little fruit forming, others quite a bit. We’ve had lower results on Anchor before, which didn’t reflect the sheer volume of fruit that we later saw develop across the island. Perhaps the trees we survey on Anchor aren’t a very good representation of the island as a whole? It’s something to look into for the future.

Results from the annual autumn counts on Anchor Island.

Results from the annual autumn counts on Anchor Island

A week later and all the counts are complete. The rimu has a huge 30% fruiting tips, which is some three times higher than the results we saw in 2015 which triggered 21 out of 22 adult female kākāpō residents on the island to breed in 2016.

Various stages of rimu fruit developing.

Various stages of rimu fruit developing

Combined these results indicate that we could be in for a huge breeding season next year. Possibly by far the biggest ever seen by the Programme! A harsh winter and strong spring winds may knock developing fruit from the trees, so we’ll recount before the summer, but we’re expecting that most females will attempt to nest. Hopefully we’ll be reporting on the hatching of many new kākāpō chicks in a year’s time!

Dusky as a tiny chick in 2016, being weighed for the first time.

Dusky as a tiny chick in 2016, being weighed for the first time


Support the kākāpō breeding season

With a big breeding season currently predicted for 2019, your support will help the season’s chicks get the best start to life and will make a big difference to kākāpō conservation. You can make a donation on the Kākāpō Recovery website.

One response to Counting rimu fruit on kākāpō islands

  1. 

    Great news and well presented. Please keep them coming!

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