Native birds in a protected breeding ground near Wellington are facing added danger thanks to a significant mast year.

Wainuiomata Mainland Island is home to a number of threated native birds, lizards, fish and plant species.

A mast year occurs when trees produce excessive fruit and seeds which attract pests, causing a boom in rat and stoat numbers.

When the food starts to dwindle through the winter the pests turn to native wildlife instead to feed their appetites.

Advertisement

Greater Wellington Regional Council Biodiversity Officer Kim Broad said they are very concerned about the situation.

"What could be a huge year for our wildlife turns the opposite, into a very poor year, and it's very likely that we'll get a lot of losses of particularly native birds."

It is set to be even worse for the sanctuary this year as several different types of trees bloomed at the same time.

"In Wainuiomata Mainland Island it's a lot more diverse forest, there's beech and podocarp forest, but this mast is going to affect a whole range of forest types so we're particularly worried about this area."

A mast year poses a local extinction risk for species such as the North Island Rifleman. Photo / Supplied
A mast year poses a local extinction risk for species such as the North Island Rifleman. Photo / Supplied

The mast year won't just affect Wellington, it could hit native bird numbers nationwide.

Broad said he is particularly worried for the North Island Rifleman.

"We aren't sure about how well it's doing in a lot of areas and this sort of mast year can really, sort of pose a local extinction to such a species without us even knowing."

The regional council has doubled down on pest control in the hopes of combating the expected high number of predators.

"It's mostly about upping the effort," Broad said

"Checking traps and bait stations more regularly and using different baits that we have in our means, so really mixing it up with all the different tools we have in our toolbox."