Eighty percent of the country's native bird species are in bad shape, with some on the brink of extinction, and the environment watchdog is recommending exploring genetic engineering and tourist taxes to tackle the problem.

Photo: RNZ

Parliamentary Commissioner for the Environment Jan Wright has released the report Taonga of an island nation: Saving New Zealand's birds, which provides seven recommendations to government.

Read the full report here: (PDF 11.4MB)

New Zealand is home to 168 species of native birds, 93 of which are endemic to this country, making them particularly vulnerable.

According to the report, 32 percent of species are in serious trouble, 48 percent are in some trouble and the remainder are doing OK.

Of the endemic birds, only 13 percent are doing OK, while 45 percent are in serious trouble, including kea, wrybill, whio, Fiordland crested penguin and takahē.

About 50 native bird species have become extinct since humans arrived in New Zealand.

What is killing the birds?

Photo: 123RF

For a long time habitat loss drove the decline of native birds, and while this was still a problem, introduced predators were largely to blame today, the report said.

"We need sustained control of predators over more large areas, so that bigger populations of birds can thrive," Dr Wright said.

Possums, rats and stoats top the most wanted list of predators and are the target of the government's Predator Free 2050 initiative, which it launched last year.

But Dr Wright said mice and feral cats were also a big problem.

"These bird killers now almost certainly number in the millions in the countryside and along forest margins."

The animals that kill birds vary across the country - apart from the top three. In the stony riverbeds of the eastern South Island, feral cats, ferrets and hedgehogs are the main predators. Domestic and stray cats are the big killers in towns and cities.

About half of the country's households have a pet cat and the number of birds killed by domestic cats is estimated to be between 5 and 11 million a year, although many will not be native.

The stray cat population is estimated to be about 200,000 and the elimination of strays is part of the country's draft National Cat Management Strategy.

Feral cats are listed in most regional councils' pest management strategies, but only four invest in widespread suppression of cat populations.

Dogs off the lead can be particularly dangerous to kiwi, and in Northland dogs are now the main killers of the bird, the report said.

Dogs running free on beaches and riverbeds during breeding season can frighten ground nesting birds and leave eggs and chicks exposed.

New Zealand is the 'Seabird Capital of the World', and humans are also unintentional predators of seabirds as they flock around fishing boats looking for food, with thousands ending up drowned in nets, caught on hooks or mortally wounded from hitting steel cables, the report said.

Bird habitats are also being destroyed by humans, deer, goats, pigs, rabbits and hares, and exotic plants such as wilding pine.

Using science to improve bird life

Dr Wright has made seven recommendations. Among those is using genetic science - to help with predator control, but also help with species survival.

Scientists in New Zealand are already looking at three areas of research into predator control using genetic science. These include: toxins that target one species of predator; a technique known as the Trojan female - where mothers produce infertile sons; and the gene drive, which increases the prevalence of a particular trait in a predator population.

The Trojan female would be bred in captivity and released into the wild to spread the mutation through wild populations.

The gene drive technology holds the potential to completely eradicate rats and other predators by creating a gene drive that only produces male offspring. The report said this held great potential but was risky, because once released it could spread by itself.

Dr Wright noted these approaches were likely to encounter opposition, but said the use of genetic science did not necessarily involve modifying genomes, and using genetic modification did not necessarily involve transferring genes from one species to another.

She was recommending the government begin engaging with the public on the potential uses of genetic techniques to control predators.

Attention was turning to managing the genetic diversity of some species to make them more resilient and increase the likelihood of their long-term survival, the report said.

Inbreeding in birds was a problem and black robin, kākāpō and little spotted kiwi all suffered from this, and Dr Wright was suggesting that "genetic rescue" was required.

This involved moving a few birds between different isolated populations to counter the risk of in-breeding, but Dr Wright said this could be expensive and risky.

She recommended developing policies to manage the genetic diversity in native birds and fauna and to develop policies for moving birds.

Tourism tax

Photo: Dept of Conservation

Tourists were visiting New Zealand for its wilderness, Dr Wright said.

Nearly two million international visitors came to this country last year and that number was projected to double in the next five years.

Dr Wright said a recent funding increase of $76m to the Department of Conservation to help with tourism infrastructure would help, but a principle of 'user pays' for infrastructure and services needed to be applied further.

She said one new source of revenue could include the department charging for car parks and for access to national parks for overseas visitors, but not for New Zealanders.

The money made from user charges could go towards covering the cost of maintaining infrastructure, which would allow more money to be spent on protecting birds and other ecological treasures, "provided Vote Conservation is not reduced".

The commissioner also suggested visitors be required to pay a levy at ports and airports to provide money for biodiversity.

Other recommendations

Dr Wright said Predator Free 2050 was a big step forward, but it did not provide an action plan and provided little detail of how the country could get to the goal. She said this was what was needed now.

She also recommended: