Noisy immigrant brings stowaways

The recent kookaburra find has enabled John Perrott and his team to make progress in their research into transmission of disease in wildlife. Photo / Martin Sykes

Dr John Perrott is the kind of dad who pickles his kids' nits.

One time, instead of treating their nits, he let them grow for a week in his children's hair so he could harvest more of them for study.

If this sounds a bit unusual, the kids understand it's all in the name of science.

Lice are part of Perrott's world and the Unitec senior lecturer in natural sciences is therefore understandably excited by a discovery he has made - he has found lice in kookaburras, something never before found in New Zealand.

Lice are vectors for disease and these ones have exciting learning potential, says Perrott, an ecologist and medicine conservationist who specialises in the transmission of disease in wildlife.

Perrott hit the news around a year and a half ago when he embarked on the great kookaburra search.

Few people had realised the big, robust and noisy Australian bird was established in New Zealand.

Now they in sightings to Perrott and his team, who then go off into the bush to climb trees and check out the nests, using "forensic ecology" to try to piece together the population numbers and find out what sort of impact the exotic birds are having on native species, and whether we need to be concerned.

The idea behind the kookaburra project was to try to find out why, unlike other Australian birds, these ones had failed to thrive in New Zealand.

Governor George Grey brought kookaburras to New Zealand in the 1860s, releasing them, along with wallabies, monkeys and even zebra, on Kawau Island in the Hauraki Gulf when setting up his own menagerie.

The kookaburra did well on Kawau but failed to take off elsewhere.

However, in the past 20 years they have established on the mainland and Perrott says indications are they have spread all the way down to the southern Waitakeres.

This is not necessarily a good thing. Kookaburras will eat just about anything and Perrott is finding quite a bit of carnage of native creatures in nests, from the remains of endangered skinks to crayfish.

In Australia, kookaburras are great eaters of snakes and other birds and when Perrott began watching them in the bush here, he was intrigued to see other birds would "mob" them.

"Mostly tui will mob them, fantails will hang around them, most birds actually will make a squawk or a pile of noise around the kookaburra.

"They seem to be not physically attacking them but putting them off, and the kookaburra just ignores them."

Kookaburras are a sit-and-wait predator, he says, a bit like a morepork, except they come out during the day.

Their eyesight is a big part of their ability to hunt, but in Australia they favour eucalyptus forest where it's very open and they can sit up high and see the ground.

New Zealand bush has a dense sub-canopy. The kookaburras can't see the ground easily, so Perrott thinks they spend a lot of time looking up instead, watching other birds.

"And so we were concerned that possibly they're predominantly bird predators in New Zealand."

In Australia they eat mostly reptiles and mammals but New Zealand results so far have indicated they're feeding mainly on invertebrates such as huhu and other beetles.

But they are eating a whole lot of other endangered species. In one nest the researchers found evidence of about nine skink and the remains of about six individual birds.

"We've also added to their tally freshwater crayfish and fish. Basically, every group you can come up with."

Even eels. He says they grab the whole eel and fly off with it to bash it to death somewhere, just as they do with snakes across the Tasman.

"In Australia they're very famous for it and in fact a lot of bushmen like to hang around the kookaburras because they have a habit of cleaning out the snakes in the area."

Perrott thinks the birds are eating whatever they can find here because we don't have the reptile and mammal densities of Australia.

He also thinks they are probably eating more native species because of our changing habitats, for reasons such as predator control measures.

And he thinks they survived on Kawau because the vegetation and sub-canopy was kept low by the other introduced species, such as wallabies and pigs, which produced habitat more like Australia.

He hopes the little lice will help figure out the population size, among other things.

They were discovered on a kookaburra which had been found in Matakana about two weeks ago after being knocked around in a bad hailstorm.

Auckland Zoo, whose kookaburra died recently, was approached to take the bird. Staff there contacted Perrott, who first screened it at the zoo-based New Zealand Centre for Conservation Medicine.

He was pretty excited when he found lice on the bird, which he then sent to Dr Ricardo Palma, a taxonomist at Te Papa, for identification.

Palma was also excited because this was the first record of lice from a kookaburra in New Zealand, and the first record of the genus Emersoniella for New Zealand. If Perrott had not discovered the lice, he says a new, unknown parasite could potentially have been introduced into the zoo.

Lice are fascinating and revealing, Perrott says, not so much because they are lice but because they can be vectors for disease.

While this louse is believed to be species-specific, living only on kookaburras, lice can also carry diseases which may not be species-specific.

"It's basic ecology these days, or basic conservation work. You screen animals to do your health checks and you look at the consequences of diseases because in the past, by not taking on disease consequences, we've stuffed things up."

An example is canine distemper. This was once considered a dog disease but now it has spread around the world, from seals in New Zealand to lions in Africa - "it's wiping out big cats all around the planet", he says.

"Our understanding of diseases in the past 15 years has gone nuts and so I'm particularly interested in when animals are introduced into an area, or when they come from an area, what are the diseases or vectoring systems they're bringing with them."

Another aspect of studying the lice is population work and genetics.

"I can look at how the lice differ genetically from, say, the lice ancestors in Australia, and from that get a measure of how distant and how long the kookaburra has been isolated from the mother population in Australia - and at the same time to have these sorts of parasites in a population, a population has to be of a certain size.

"From finding the parasite we can glean a whole pile of information about the population dynamics of the kookaburras themselves."

This is all very important in how we might decide to manage the kookaburra.

"They must have been established in large enough numbers to maintain a parasite share for 150 years, so really it's just another avenue for unravelling some of the mysteries behind the population management of kookaburras in New Zealand."

The Department of Conservation had targeted the birds as potential pests, based mainly on information from Australia, because when they were translocated to Tasmania in 1890 they had large impacts on some of the smaller bird species.

Tests have yet to be carried out and though it is possible, Perrott doubts any potential disease will spread to other animals. But learning from this vector system can, perhaps, help inform us about other species affected by other vector systems

"It's an area which has been really data-poor for a long time and it's only since the emergence of zoonotic diseases like Aids, swine flu and avian flu that people have started to take diseases more seriously at the ecological level, so we're riding a wave of public interest in disease dynamics."

The combined studies may also reveal whether all kookaburras in New Zealand have come from a single population or whether some have "self-introduced", where they have made their own way here.

Other much-loved native species are actually self-introduced, such as the morepork which came from Australia about 1000 years ago.

Understanding how the kookaburra got here is important. Perrott says there is no point going out shooting them all if within the next five years more will turn up

"It might just be better trying to understand how they're operating and what we can do to try and protect species from them rather than just trying to eliminate them."

Dr Perrott still wants kookaburra sightings. If you spot one, contact him at: jperrott@unitec.ac.nz

KOOKABURRA
* Introduced in the 1860s
* Failed initially to thrive except on Kawau Island
* Now have spread to the mainland
* Eat native species like skink
* Mob other birds
* Brought with them a lice never before found in New Zealand