Bird life in the Brook Sanctuary can be seen and heard within the fenced perimeter.

A tree collapsing on the Brook Waimarama Sanctuary's protective fence had staff and volunteers of the park acting fast.

The large tree damaged the fence during ex-cyclone Fehi's wrath on Thursday but systems in place meant the fence was back up within a few of hours.

The Brook Waimarama Sanctuary trust coordinator Kat Willcocks said it was "really no biggy".

LUZ ZUNIGA The Brook Sanctuary mop-up map.

She said all teams were "standing by" during the harsh weather conditions.

As soon as the tree breached the fence, the fence's electronic monitoring system alerted the park's staff.

"We had ... a good few vehicles full of volunteers who went up to fix the fence."

In conjunction with all hands on deck, a series of monitoring devices were placed inside the fence which would be checked every day for 10 days.

"So far we've monitored that since the breach and we have nothing.

"There's a pretty good web of detection."

Meanwhile, the sanctuary is on track for becoming a haven for native wildlife after "zero detection" of the most damaging pests.

Close monitoring has been carried out on the 691 hectares of fenced sanctuary since the final brodifacoum drop October last year and the Brook Sanctuary general manager Hudson said the results were "very encouraging".

An eight-week programme of weekly checks has been completed, which is the first of two stages.

The checks involve a grid of monitoring 2700 stations along tunnels with detection devices.

The tunnels attract any mammals present with lures including peanut butter or rabbit meat. An ink pad with a paper card inks the pests feet to leave footprints.

Dodd said the goal was to have no mammals present.

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There had been zero detections of rodents, stoats, weasels and ferrets, he said.

​"They're the target species."

He said the results were "as good as you could have hoped for".

Time is yet to tell if the pests have been wiped out completely.

"It's not 100 per cent conclusive."

He said there were other pest species that could be present so they were checking the site for any surviving pests.

Hedgehogs, possums and a hare had been detected but he said after trapping 12 hedgehogs, they were down to "barely any detections".

Attention was being turned to "a couple" of possums which would be "straight forward to track and trap".

"We're mopping up the few remaining pest mammals in the site and it's looking very positive."

Dodd said he understood some people might have thought "most of the landscape must be littered with carcasses".

"That's not the case."

"When any mammal feels sick, they go and hide, usually to their lair ... that's where they meet their fate. You can actually think of it as self-burying themselves. Largely they are under ground and out of sight and becoming compost."

The pest clean-up has had a positive impact on the wildlife within the park.

"I'm happy to report that there have indeed been sounds of weka and morepork in the site since the operation. All is well there."

He said the focus of the project was to restore the eco-system, bringing back bird life, invertebrates and reptiles.

"This is the next milestone of achieving the vision of the project. Restoring the eco system right on Nelson's doorstep ... will allow species to breed and thrive and then spread out from it ... follow the green fingers."

The next phase of monitoring will involve monthly checks, continuing for several months.