The reserve is also a danger zone for invading mammals thanks to a series of mustelid, possum and rat traps. The past year's haul included 36 possums and 35 rats, including a giant Norwegian rat caught earlier this month.
"Since we started trapping in 2006, we've caught 162 possums, 94 rats (including nine Norway's), 61 mice, 12 hedgehogs and three mustelids," Gerald said.
"The bush is looking great with lots of seedlings coming up, so it's definitely paying off."
And it's not just the trees that are benefiting from all the hard work.
Of particular delight to Gerald has been a pair of moreporks (ruru) that moved into a nesting box he made and erected last year.
"I was on holiday in Germany when my son rang to tell me that Morkie (the nickname Gerald has given to the little owls) had moved in. I couldn't wait to get home," he said.
The moreporks produced one chick, Morkie Junior, now almost fully-fledged.
It's been a rewarding journey but one tinged with sadness since Dave passed away in December, 2011. He is remembered as a humble man, who liked to get on with it.
Dave was a stalwart of conservation who spent his retirement involved in all sorts of conservation efforts, including helping with the taiko project (saving the critically endangered magenta petrel) on the Chathams, but his main passion was Taumarumaru Reserve. A boardwalk over the wetland at the entrance to the reserve is among his achievements.
His visits to our office were frequent. He was persistent in his ideas to improve the well-being and enjoyment of the reserve for the community. It was hard to say no to him.
Gerald still misses his mate but he's determined to keep the good work they have achieved going.
"I sorely miss his company," he said.
"We were a good team and worked in harmony. It just goes to show what a couple of old guys chipping away with a few tools can do. The main thing is having the time.
And there's always plenty more to do, as winning the war on invasive pests is a long-term commitment. Cooper's Beach homeopath Shelley Rademacher trims back weeds around the trees when she can and has erected a little sign to encourage people to take their rubbish home with them.
Gerald is as enthusiastic as ever but doesn't mind admitting he's happy to share the workload with any other like-minded folk keen to lend a hand.
"Bruce Collett helps me with the weed spraying when he can but there's always work to do checking the traps, weeding and the odd bit of planting, although most of that's finished now," he added.
Gerald would love to hear from anyone with some spare time and willing on 406-2201.
