Ulva Island – a decade on

A decade after it was declared pest-free, Ulva Island is more than a conservation success story. Research on Ulva is expected to be critical for managing other pest-free havens, and its open sanctuary status is providing a much-needed boost to tourism and the local economy, Kathy Ombler finds.

All in the family

 Dr Ian Jamieson is spearheading research on the introduced robin and saddleback populations of Ulva Island.

He says many re-introduced populations are founded with small numbers of individuals, and there tends to be little or no subsequent gene-flow between these and mainland populations (if they exist).

“This raises questions about the effects of inbreeding and loss of genetic variation on the … viability of island sanctuaries.”

Genetic diversity is the main ingredient upon which natural selection operates; loss of genetic diversity will mean a reduction, for example, in a species’ ability to defend itself against new pathogens and disease.

While scientists have plenty of theory about the effects of loss of genetic diversity, there is relatively poor understanding of how this is manifested in real populations. Island sanctuaries such as Ulva are ideal places for conducting research to try to answer these questions in a “real-life” situation.

Since 2001 researchers have tracked saddleback and robin populations on Ulva Island.

Each season researchers find all the territorial pairs and any single birds each spring, monitor their activity to find nests, record their nesting success, and colour-band any nestlings – a tricky process but one that yields vital information.

“My students and our hard working volunteers have become some of the best saddleback nest finders in the country!” Jamieson says.

These field observations are then entered into a software programme that draws the birds’ “family trees” and calculates how inbred each individual bird is.

Jamieson says the main aim of the research is to estimate the rate of increase in inbreeding and what its consequences are, if any, for the viability of each population.

It is hoped that the research will provide guidelines for Department of Conservation managers for managing inbreeding and loss of genetic diversity in other relocated populations.

 

Imagine New Zealand how it used to be. Imagine the forests before the ravages of introduced animal pests took their devastating toll, before the centuries-old trees were burned and felled, and the forests resounded with native birdsong. Ulva Island, nestled in Paterson Inlet/Te Whaka a Te Wera of Stewart Island/Rakiura, has to be as close as it gets today.

The giant podocarp forest of Ulva was never felled. There were never browsing possums, nor goats, nor bird-eating stoats and ferrets on the island. Deer and rats were the only “aliens” let loose to do their dastardly deeds - which they did with a vengeance until 1997 when, following one of the largest rat eradications undertaken in New Zealand, the 260-hectare island was declared pest free.

Eradication cleared the way for the re-introduction of native species that had been long absent from Ulva. Stewart Island robin were brought in from nearby Freshwater River forests. South Island saddleback, mohua (yellowhead) and rifleman were re-introduced. The (not so common) common skink was the first reptile to be re-introduced, and further reptile releases are in the pipeline.

For Brent Beaven, the Department of Conservation’s Biodiversity Manager on Stewart Island/Rakiura, the highlight of Ulva has been the island’s ability to regenerate itself.

“No one really believed the impacts rats were having on the forest under storey. Now when we walk around we see layers of forest that weren’t there before. The diversity of the forest has expanded and it’s ongoing. Every year, as the trees’ ability to fruit increases and you get more capacity for birds, the diversity grows.”

Ulva Island Charitable Trust Chairman, Peter Goomes, says every year there are more birds on Ulva.
“There are more kakariki, more kaka - and what is really good is that there is opportunity for people to come here and see them.”

Other pest-free islands, such as Whenua Hou and Breaksea, aren’t accessible, but people can easily get access to Ulva and its easily walkable tracks.

Growing numbers of nature lovers and birdwatchers from around the world are coming to Ulva Island. With the decline of Stewart Island’s fishing industry, the community is increasingly reliant on nature tourism to sustain the local economy.

There was an added boost in 2006 when kakapo Sirocco was placed on public display for 10 weeks on Ulva – this unique opportunity to “meet” a kakapo was an international drawcard, and there are plans to repeat the experience this year.

The Sirocco experience was a good example of how conservation and nature tourism can have a strong, symbiotic relationship, Goomes says.

The community-based Ulva Island Charitable Trust was established in 1998 to help upgrade of tracks and facilities, which greatly improved visitor access.

The trust went on to help fund bird releases, monitoring, research, the Kakapo Encounter, and a promotional DVD celebrating the 10th anniversary of Ulva’s pest-free status.

Brent Beaven says long term research by the University of Otago’s Department of Zoology, which has a research facility based on Ulva, is looking into the genetic diversity of introduced species and effects of inbreeding, focusing on robin and saddleback. Information gathered here could be vital for management of species introduced to other pest free areas.

“We always think they are safe on the island, but is that really the truth? If you take 30 birds of one species to restart a population does that give you enough diversity to sustain a species long term? We hope we can find answers to these questions on Ulva.”