Mammal mafia waging war on native birdlife

16:00, Dec 04 2009

New Zealand's "mammal mafia" has been accused of devouring more than 26.5 million birds in native forests a year.

And the death toll of native birds is even higher when attacks in other habitats are included.

Hamilton-based Landcare Research scientist John Innes tallied the damage wrought by rats, possums and stoats, who he called a gang of mammal mafia, to illustrate the threat to the country's native wildlife.

And he said it was time opponents of 1080 "got real about the facts".

"Most endemic forest birds are disappearing because of predators – 1080 opponents should get their heads around the fact that while they complain about cruel deaths, millions of forest birds are being killed by mammals every year."

Statistics quoted in a New Zealand Journal of Ecology and published on-line this month, were used to produce the multimillion death toll, which Mr Innes said was an under-estimate and did not include the adult, usually a female, which had been incubating the eggs or caring for the chicks. It also did not include introduced species such as blackbirds and thrush.


Mr Innes said forest covered 23 per cent of New Zealand, an area totalling 5.98 million hectares. He said if there were five native bird nests to each hectare in any nesting season, that was 29.9 million nests. Of those, 73 per cent failed – a total of 21.827 million nests and, at an average of two eggs per nest, a total of 42.654 million chicks which failed to fly from the nest.

Predators are blamed for 61 per cent – 26,628,940 – of chick and egg losses.

Mr Innes said the mammal war on birds went unnoticed because it occurred at night at the top of trees. "There has not been one published eye-witness account of a ship rat killing a bird, yet it's been going on since the ship rat arrived here, and the kiore (native rat) before then. There is nowhere that a bird can lay a nest that a rat can't get to. That's why they are such pervasive agents of change."

Mr Innes' comments follow on from a series of 17 marches, including one on his home patch Hamilton, calling for an end to aerial drops of 1080 targeted at possums.

Opponents said the Government should use different methods to control or trap pests because aerial drops hit animals which had not been targeted.

New Zealand uses 80 per cent of the world's production of 1080 and the Environmental Risk Management Authority (Erma) regards it as a "necessary evil".

Taupo District Council has already banned aerial drops. Mayor Rick Cooper said the operations were uncontrolled and the risk to the environment and waterways too great.

But Mr Innes said he re-mained frustrated that people still could not accept the evidence that mammals were destroying the vast majority of nestings attempted by endemic birds and "we have this fabulous toxin" which could help.

Levin photographer David Mudge has, for more than a decade, illustrated the carnage in New Zealand forests by producing photographic evidence to condemn the mammals.

The publication of one of his pictures, showing a rat eating a fantail, upset some Waikato Times readers in 2007. But Mr Innes wanted to see more such pictures published.

Mr Mudge has been taking wildlife photos since 1983 and has become an expert in getting incriminating evidence against mammals.

Waikato Times