biology

The Mysterious Adzebill

New Zealand was once home to many flightless birds. Some, like the moa, are well-known, but others, like our flightless ducks, geese, and owlet-nightjar, are familiar mostly to palaeontologists. One bird that deserves to be better known is the mysterious adzebill.

1. Adzebill Martinson

A North Island adzebill (Aptornis otidiformis) eyes up a tuatara in a 2005 painting by Paul Martinson.
Photo: Te Papa / CC-BY-NC-ND

There were two species of adzebills, Aptornis otidiformis in the North Island and Aptornis defossor in the South. Both were huge. When their bones were first discovered, they were mistaken for a small moa. Fully-grown birds would have weighed perhaps 20 kg, larger than a swan or pelican.

Adzebills had massive heads with heavy down-curved beaks. The beaks tapered to a point, and Dr Richard Holdaway, who coined the name “adzebill”, once confessed to me that “pick-bill” would have been more accurate. The robust vertebrae in their neck would have anchored strong muscles and allowed them to deliver a powerful blow.

These birds also had massive feet, with strong tendons, that would have made them good at digging. For some time biologists debated what they ate. Did they dig up roots, pluck leaves or break apart rotten logs? Their beak wasn’t hooked like a bird of prey.

A technique called stable isotope analysis which lets us analyse animals from the composition of bone – you are what you eat – revealed that adzebills were carnivores. We can imagine them tearing open trees for huhu grubs, plucking lizards or baby birds off the forest floor, digging up giant earthworms, and excavating tuatara, or even nesting seabirds, out of their burrows.

A second mystery was what adzebills were, exactly. They didn’t resemble rails like the weka or takahē, and for some time were put in their very own family. Some ornithologists thought their closest relative was the flightless kagu of New Caledonia. Others thought it belonged with chicken-like South American birds called trumpeters. The debate continued fruitlessly for decades.

Alex Boast is a PhD candidate at the University of Auckland, working on ancient DNA. Improved techniques now allow us to recover and examine fragments of DNA from bones and eggshell of extinct birds, not enough for Jurassic Park cloning, but enough to construct a family tree and determine their nearest relatives. Alex analysed adzebill DNA and compared them to numerous other birds, and the results suggest that adzebills are not kagus, or trumpeters. They are flufftails.

2. Flufftail Keugelmans

The white-spotted flufftail (Sarothrura pulchra), painted by John Keulemans in 1894. This delicate little bird seems to be the adzebill’s closest living relative.
Ref: Wikimedia Commons

Flufftails (nine species in the genus Sarothrura) are secretive ground-dwelling birds about the size of a starling, rusty brown and spotted. They do indeed have fluffy tails. What’s unusual is that flufftails are all found in Africa, and on the island of Madagascar, nowhere near New Zealand.

Africa and New Zealand were once connected as part of the supercontinent Gondwana of course, and fossils tell us that adzebills have been here for millions of years, plenty of time for their ancestors to get here and evolve into a giant flightless predator. Intriguingly, the kiwi seems to have done the same thing. Its closest relative is another African species, the elephant bird of Madagascar. The difference is, while one flightless bird survived the arrival of human beings and became the symbol of New Zealand, the other was wiped out. The not-so-mysterious adzebill is now mostly forgotten.

 

Dr Mike Dickison is curator of natural history at the Whanganui Regional Museum.

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Discovering new species

When a new species of plant or animal is discovered it’s a big news story, but the secret amongst biologists is that it’s actually easy to find a new species. It’s hard to convey to people just how many species remain to be discovered, and how few people there are left looking for them.

Undiscovered jumpers: There are over 50 species of cave wētā, or tokoriro, in New Zealand, which, despite their name, live mostly in the forest. So many new species are being discovered that there is a backlog waiting for the few entomologists who study wētā to find the time to describe and name them. Creative Commons BY-NC, Jon Sullivan / Flickr

Undiscovered jumpers: There are over 50 species of cave wētā, or tokoriro, in New Zealand, which, despite their name, live mostly in the forest. So many new species are being discovered that there is a backlog waiting for the few entomologists who study wētā to find the time to describe and name them.
Creative Commons BY-NC, Jon Sullivan / Flickr

There are probably undescribed species living in your backyard. Entomologist Willy Kuschel spent 15 years collecting beetles in the Auckland suburb of Lynfield. He found 982 species of beetle, far more than anyone would have suspected could be living 10 kilometres from the central city. Amazingly, 150 of those beetles were new to science. Nobody had noticed them because nobody had looked.

There are probably species to be discovered in Springvale and Aramoho, but if I wanted to find one I’d start at Bushy Park, one of the last remnants of lowland forest in this part of the country. Bushy Park has never had biologists do a comprehensive survey of its insects, snails, and spiders, so we have no idea what’s there. Collecting a scoop of leaf litter from the forest floor and picking through it might well reveal species surviving there and nowhere else.

The stick that moves: A new species of stick insect found only on the Poor Knights Islands was recently named Clitarchus rakauwhakanekeneke, in conjunction with local iwi Ngāti Kuri. Its Māori name means “the stick that moves”. Thomas Buckley / Landcare Research

The stick that moves: A new species of stick insect found only on the Poor Knights Islands was recently named Clitarchus rakauwhakanekeneke, in conjunction with local iwi Ngāti Kuri. Its Māori name means “the stick that moves”.
Thomas Buckley / Landcare Research

The scientists who do this sort of survey and name new species are called taxonomists and their work is the foundation of all conservation policy and ecological research; you have to be able to list and name the living things in an area before you can measure how they’re doing or develop a management plan. Taxonomic research has always been the mainstay of museums, which have large comparative collections. But museums all over the world have been cutting back, and New Zealand is no exception.

 

When I was a lad I was mad keen on lizards, and conventional wisdom was that we had a dozen or so species in New Zealand. Since we started looking closely at lizards and their DNA, it turns out there are actually about 100 species, but there are only a handful of scientists able to formally describe them and give them names. The most recent field guide to native lizards has to refer to fairly-widespread species with labels like “Genus B species 1”, because we don’t have enough taxonomists.

Thambotricha vates, a Latin name that translates as “wonder-haired prophet”, has been found by entomologists for the first time since 1996. This elusive moth has only been seen 15 times since it was described and named in 1922. Creative Commons BY-NC, XXXXXXXXXXX / Flickr

Thambotricha vates, a Latin name that translates as “wonder-haired prophet”, has been found by entomologists for the first time since 1996. This elusive moth has only been seen 15 times since it was described and named in 1922.
Creative Commons BY-NC, XXXXXXXXXXX / Flickr

Even after a species is described, we don’t know necessarily know anything about it. Recently a small moth, Thambotricha vates, was caught by Landcare entomologist Robert Hoare. It had last been seen in 1996 and only 15 specimens had been collected by scientists since it was first described in 1922. Because it’s found from Nelson to Katikati, it probably isn’t rare; we just don’t know its habitat. Although the media treated this rediscovery as a big story, it isn’t all that exceptional. There are over 1,700 species of moths in New Zealand, and some of our 10,000 insect species have almost certainly been seen just once, by the entomologist who described them.

 

In NZ there are many species of native earthworms, some of them gigantic. In all the gardens, parks, and farmland of NZ the earthworms are just a few introduced European species. Unfortunately we know very little about native earthworms; many have been found from deep in the subsoil, living in a single patch of native bush. Thirty species occur only on a single small island each, but 102 species are listed as “data deficient”. They could be widespread, or on the verge of extinction – we don’t know. And there are surely native earthworms still unknown to scientists, which might go extinct before they’ve even discovered.

A new species washed up on the beach: George Shepherd, Curator at the Whanganui Regional Museum in 1933, measuring the skull of the beaked whale that was eventually named Tasmacetus shepherdi in his honour. Whanganui Regional Museum Collection 1805.296.2

A new species washed up on the beach: George Shepherd, Curator at the Whanganui Regional Museum in 1933, measuring the skull of the beaked whale that was eventually named Tasmacetus shepherdi in his honour.
Whanganui Regional Museum Collection 1805.296.2

Not all new species are moths and worms. There are still discoveries to be made in the deep sea, even of large marine mammals. The Whanganui Regional Museum still has the skeleton of a beaked whale that washed up on the beach near Hāwera in 1933, and was collected by George Shepherd, the Curator at the time. He recognised it was unusual, and sure enough it turned out to be a new species. Shepherd’s beaked whale (Tasmacetus shepherdi) lives in deep water far from shore, in cold southern seas, so live animals have been seen only a handful of times. Most of what we know about them comes from stranded specimens.

 

New techniques can also help discover species that were hiding in plain sight. When the DNA of kiwi populations all over New Zealand was compared, the birds around Ōkarito on the West Coast turned out to be very different from other brown kiwi. Collectors in the 19th century had noticed this, and used the name rowi to distinguish them from other kiwi. The DNA evidence was enough to establish them as a new species, Apteryx rowi, numbering just a few hundred birds in one patch of forest. They now have their own captive breeding program.

Saving a subspecies: The Hector’s dolphin (Cephalorhynchus hectori) has North Island and South Island subspecies that can interbreed. The North Island form, or Maui dolphin, is in danger of extinction, but saving it shouldn’t be as high a priority as all the other actual endangered species in New Zealand. Creative Commons BY-NC, Earthrace Conservation / Flickr

Saving a subspecies: The Hector’s dolphin (Cephalorhynchus hectori) has North Island and South Island subspecies that can interbreed. The North Island form, or Maui dolphin, is in danger of extinction, but saving it shouldn’t be as high a priority as all the other actual endangered species in New Zealand.
Creative Commons BY-NC, Earthrace Conservation / Flickr

Without the attention of taxonomists the rowi might have quietly gone extinct while we were distracted by showier things like Maui dolphins (which are not actually a distinct species, just the Hector’s dolphins that happen to live in the North Island). The worst scenario is discovering much later, from museum specimens, that something collected a century ago is both a distinct species and no longer to be found in the wild. How many species have we already lost, species that we’ll never know about, because we didn’t notice them in time?

 

Dr Mike Dickison is Curator of Natural History at the Whanganui Regional Museum.