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Scientists studying fossilised poo from New Zealand’s kākāpō, have discovered the large, flightless nocturnal parrot ate a much broader variety of plant foods in the past.
The findings – which include that the kākāpō’s diet also once included beech leaves and seeds and beech mistletoes – offer crucial insights for its conservation, increasing the number of potential sites where bird populations could be re-established. It suggests beech forests could be potential habitats.
While the birds rely heavily on rimu forests today, the study published in Frontiers in Ecology and Evolution dramatically increases the threatened species’ known food plants – increasing the variety of plant orders by 69% and families by 108%.
Lead author Dr Alexander Boast says the research was sparked by interest in the kākāpō as an endangered species, and the unique source of information in the form of coprolites (or, fossilised bird poo) preserved in caves around New Zealand.
Boast says the kākāpō is a “weird fascinating bird”. It is the only flightless parrot in the world, and also the heaviest. They’re nocturnal and are known to have a strong scent which has been described as musky, like an old violin case, he says.
The extensive fossil record, in the form of coprolites, is also unique for an endangered species (with kākāpō coprolites often found alongside samples from the extinct Moa).
Since human arrival, the parrot’s population has crashed, Boast says. In part because the bird is not very good at breeding and is extremely vulnerable to mammal predators. “It’s main approach, when predators are nearby, is to stay very still”, he says.
With the kākāpō population currently at approximately 250 individuals on three small offshore islands, co-author Dr Jamie Wood says every piece of information helps.
“We know that kākāpō used to be right across New Zealand. We find their fossil bones in caves, from the top of the North [Island], right down to the bottom of the South. So they were one of the most widespread birds before human arrival,” he says.
The last two wild populations of the parrots were based in Fiordland and Stewart Island. This means knowledge about kakapo diets today is based largely on the restricted vegetation communities for those last two remaining populations, Wood says.
Using DNA analysis and radiocarbon dating, the scientists from the University of Auckland, Manaaki Whenua Landcare Research and the University of Adelaide, analysed 125 kākāpō coprolite samples gathered from caves across the South Island. Samples cover a huge timespan, ranging from hundreds of years old through to more recent.
The results broaden the potential conditions for the bird’s breeding.
Kakapo today tend to only breed when just one tree – Rimu – is fruiting, something that only happens every two to five years. “This a big speed bump in getting the populations up,” Boast says.
But the large amounts of Southern Beech – a species which cover about 50% of New Zealand’s forest today – in the coprolites, and some similar characteristics to rimu, suggest the possibility it could play a similar role in kākāpō breeding.
“In some of the caves where we found the coprolites, we also find egg shells of kākāpō and chick bones. So, we know they were breeding in those sites,” Wood says.
The research findings offer potentially valuable information for kākāpō conservation, as it increases the number of places where bird populations could be re-established.
Further kākāpō coprolite research could reveal even more about its diet, with the next step in analysis investigating what types of fungi the birds were eating.