The four-egg clutch of kōkako eggs is the largest clutch ever recorded for the species. But a storm killed the babies inside.

A mother kōkako, who laid the largest number of eggs ever recorded for the species, has had her little chicks killed in a storm.

Only one of the four eggs in a kōkako nest found in the 1300-hectare Parininihi Forest had hatched, but Tiaki te Mauri o Parininihi Trust project manager Conrad O'Carroll said the baby bird did not survive stormy weather last month.

"It got wet and cold and died," he said.

Conrad O'Caroll/Supplied Tiaki te Mauri o Parininihi Trust have found this last breeding season to be successful with 13 nests discovered, though not all chicks have survived.

"The female left the nest. One of the other eggs was cracked, so we left it, and the other two we took away for analysis."

Last year, 20 kōkako were taken to the forest from Tiritiri Matangi Island, marking the return of Taranaki kōkako to the region after an absence of about 18 years.

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Tiaki te Mauri o Parininihi Trust/Supplied Another 20 kōkako birds will be introduced to North Taranaki in an effort to diversify the genetic diversity.

Since the release in May and July, surveyors have spent "most days" tramping dense bush and walking along steep gullies to determine the birds' territories.

The conservational trust, which works to boost kōkako population numbers in North Taranaki, has found 13 nests with 37 eggs since November.

During the breeding season kōkako females, eggs and chicks are very vulnerable to predation by rats, stoats and possums.

Conrad O'Caroll/Supplied Surviving kōkako chicks are banded so that their welfare can be monitored.

When surveyors find nests, O'Carroll said extra methods of protection are put in around the nest.

"Effectively, we set up a wall of defence," he said.

"This includes setting up at least 20 rat traps baited with Nutella or peanut butter, A24 self-setting rat traps, stoat traps and various types of possum traps."

However not all baby birds have survived.

The record-breaking clutch (nest of eggs) was just one of the failed nests.

Strong winds and rain from stormy weather before and during ex-cylcone Gita has left some nests "battered" and hatched chicks dead from the cold.

Unsuccessful eggs have been taken away to analyse their nutritional properties in the hopes of discovering what has helped paired kōkako produce the high number of eggs. It will take six months to get results.

O'Carroll said kōkako typically lay one to three eggs, but majority of the nests in Parininihi have had three.

However, he added, some have been unfertilised and "a lot have been killed by predators".

"Two nests were raided by a stoat or a rat and a few have been taken by falcons.

"Falcons are natural predators, so there isn't anything we can do about that.

"Our biggest focus right now is to lower predator numbers, and to do that we need funders."

Despite the disappointing discoveries, there were a lot of positives to take away from this season.

One of those included the length of season, which typically ends earlier in February.

But healthy active nests have been found as recently as yesterday.

"This last one we'll be keeping a close eye on," O'Carroll said.

"We didn't expect to find any more. We're breaking all sorts of records."

Next month another 20 kōkako will be moved from Pureora to the Taranaki forest to add to the genetic diversity in the area.

O'Carroll said this would be about the same time as young birds fledging, or leaving the nest.

"It's going to be a very busy time for us."