The road-hugging habit of a rare flightless bird could put a spoke in the wheel of the Department of Conservation's plan to open the roads of Auckland's Rangitoto and Motutapu Islands for a year-round mountain biking venture.
In a bid to cash in on the popularity of the one day a year in which mountain bikers can use the islands - in the Dual multi-sport event - the department proposes a three-year trial of a commercial concession for bike hire and guided tours.
However, the proposal has outraged the Auckland Council parks recreation and heritage forum, which says it will kill off the Dual event, which raises $50,000 a year for the Motutapu Restoration Trust.
Councillor Christine Fletcher, who also chairs the trust, said volunteers had planted thousands of trees for translocated birds such as the endangered takahe, saddleback and Coromandel brown kiwi.
"The ecological programme has put takahe on the doorstep of Auckland and to encourage mountain biking is a recipe for disaster.
"Takahe are friendly and their favourite thing is standing in the middle of the road," she said.
The islands are a pest-free breeding sanctuary for 16 takahe - 6 per cent of the country's takahe population. The islands are reserves administered by the department.
Five years ago, it granted the trust and events company Total Sport a joint concession to hold the Dual traverse of the islands, which are linked by a causeway.
Mrs Fletcher said the event was tightly controlled and monitored to ensure no harm.
"I know DoC is under pressure to be generating further revenue sources but to open up to mountain bikers willy-nilly would go against the work of the last 20 years."
However, the council's Auckland Tourism, Events and Economic Development wants to work with the department to unlock the potential of Auckland's natural assets.
It sponsors the Dual and said mountain biking on the islands was an example of DoC initiatives that would draw visitors to the region and stay longer and spend more.
Dual event manager Nick Carroll said the next event on March 23 had drawn 2000 entries, of which 600 would be on mountain bikes and the rest would run or walk the islands' trails.
About 100 marshals would keep competitors and 300 spectators confined to a marked route.
All bikes came to the island by separate ferry and were cleaned and disinfected.
The department's proposal to allow a mountain biking concession is in its draft conservation management strategy which is open for public comment until March 15.
DoC Auckland conservator Sean Goddard said the Dual had no impact on the islands' terrain, vegetation or wildlife.
This had prompted DoC to float a new proposal to have a three-year trial of managed biking.
Bikes would be hired on the islands and able to be ridden in groups limited to eight on designated roads on Rangitoto and on nearly all roads of Motutapu and some tracks during certain times of the year.
Rangitoto & Motutapu Islands
130,000 visitors a year to reserves & sanctuary
25-minute ferry ride from downtown Auckland
6 per cent of NZ's critically endangered takahe population breed there
2000 entries for Dual bike, run, walk event March 23
$50,000 of fees pays for planting trees