They've fenced it, sprayed the gorse, dug out ponds - and most recently dug a new long-drop toilet.
"The land we are on is pretty special," Mr Shearer said. "There are brown kiwi as well as the rare pateke duck (brown teal), so we've dug some ponds and fenced off areas that, hopefully, they'll inhabit. And it's a couple of minutes' walk to the beach."
Their caravan was basic, he said.
"It's a classic and has everything we need for a great beach holiday. It's even got the same lino on the floor that we had in our family home when I was a kid.
"It has no running water, no power, no phone, just a stream that runs beside us with a small pond and waterfall to wash in."
With their children Vetya and Anastasia - now teenagers - the Shearers have been holiday camping for 15 years, sleeping in tents before buying the caravan.
Mr Shearer, 56, who is Labour's spokesman for foreign affairs and energy and resources, said that even when the family were based overseas, as humanitarian workers for Save the Children Fund and then the United Nations, they returned to Northland for their summer holidays. They visit their section a few times a year.
"It's just three hours from Auckland so quite do-able for a weekend, and a great way to catch up with the kids without the usual distractions," Mr Shearer said.
"We've been there for a handful of weekends this year, mainly the statutory ones, but the main holiday happens over Christmas and New Year."
Activities include surfing with his son - and their dog paddling alongside them.
"And we have a dinghy with an outboard motor so we fish from time to time," Mr Shearer said.
"Other than that, there's a fair amount of reading, guitar-playing and hanging out with whoever is around."
He said they would like to eventually put up a building on the section that would be more comfortable in winter, but eco-friendly and "off the grid". "But right now, it's our little bit of paradise."
Public records show the Shearers own a house in Pt Chevalier valued at $1.83 million and a rental property in Avondale worth $450,000.
The man who replaced Mr Shearer as Labour leader, David Cunliffe, and his family were staying at a friend's bach in the Nelson/Tasman area this summer, his spokeswoman said. They did not own a holiday home.
"His family goes to a range of holiday spots," the spokeswoman said.
"Their favourites are Northland, Coromandel, Golden Bay and the South Island high country for tramping."
