Head ranger Adam Willetts with one of this year's surviving grey-faced petrels.
Head ranger Adam Willetts with one of this year's surviving grey-faced petrels.
After a single stoat took the lives of all 10 grey-faced petrel chicks in 2020, undoing the hard work of devastated Bream Head Scenic Reserve Trust workers, this year, they celebrate a victory.
Nine chicks took flight in December and January, marking the third successful breeding season since the birds' 2015 re-establishment at the 800ha predator-free Bream Head Scenic Reserve located at the tip of the Whangārei Heads peninsula. Their survival is the result of a hard-hitting predator control and monitoring programme developed in response to loss of chicks to predators in previous seasons.
Trust head ranger and project manager Adam Willetts said the grey-faced petrels returned to breed at Bream Head in the 2015/2016 season, one of only a few known, naturally occurring mainland breeding sites for the large grey seabirds.
Known to Māori as oi, they hadn't been seen on the reserve for decades after humans and animal predators wiped them out.
"I discovered them on the eastern end after we'd been looking for them for a long time. We hadn't been there and suddenly I noticed. There had been old burrows there but they were not active."
He said some of the burrows, ranging up to 2.5m deep, date back decades and, while it was possible the odd adult grey-faced petrol had been inhabiting the reserve over the years, if it weren't for the intensive predator control programme and ecological restoration work of the Bream Head/Te Whara Conservation trust, they would have become locally extinct from the reserve.
"They were close to the brink of extinction. The year earlier, we'd put in rodent and stoat control in that area. That eastern tip was the last to go in July 2015 when we finally put in the last of the intensive predator control over that entire reserve. Before, that, they'd probably been trying to come back but getting killed."
He said the first two seasons saw the survival of the eggs due to rat eradication. However, there were remaining stoats at the reserve, which took out the chicks pre-fledging.
Following this, there were two 100 per cent successful breeding seasons but, at the beginning of 2021, all 10 chicks on the study site were eaten by a single stoat, as distressingly played out on video footage from cameras at the burrows' entrance.
"It was awful," said Willetts, still affected by the outcome.
However, the team intensified their eradication plan which involved continual trapping and baiting, and the introduction of new monitoring technologies, catching two large stoats in the process last winter.
One of the grey-faced petrel chicks prior to taking flight. Photo / Shannon Courtenay
As a result, 10 chicks hatched, though video footage detected one leaving the burrow early while its parents were on extended leave and Willetts suspects it may have fallen off the cliff before learning to fly.
"This year the chicks were really plump really early. But sometimes the parents don't come back because they get caught up in big storms at sea or they might have ended up in fishing lines."
Extensive video monitoring allows Willetts and other rangers to witness the petrel chicks exiting the burrows and carrying out pre-flight exercises around 10 days leading up to take-off.
"It's quite incredible, they open up their wings, preen out the downy chick feathers and get their flight feathers coming through. It's quite a big effort."
And then, over the course of two months, they watched all nine individually take flight.
"It was a huge sense of relief as we had been intensively protecting and monitoring the eggs and chicks since July. I felt immense pride in the trust programme too," he commented.
He said the chicks fly offshore in search of food, such as squid, before heading to the northern Tasman sea. They were expected to return to breed in around four years. Despite the burrows' long tunnels, the team were able to reach and apply lifetime bands to seven of the nine chicks.
Planning for the next round is already beginning, volunteer co-ordinator Jenny Lawrence said. The cycle begins when the grey-faced petrels start checking out their possible burrow nesting sites in autumn, before nesting in winter. The incubation is shared before the parents take flight in search of food, leaving the eggs and chicks vulnerable to predation from August for several months.
"It's a tense time!"
Said Willetts: "We make every effort to help these special seabirds breed again on the mainland. We use all the current predator control tools available in the reserve, such as automated lure dispensers, infra-red cameras, tracking devices, different baits and traps. It is intensive work, but it's so worth it when you see the chicks fledge on camera - that's a very satisfying feeling for the team.
"It will be great to welcome these noisy birds back in approximately four years' time when they will return to breed themselves on Bream Head/Te Whara."
Grey-faced petrels, along with other seabirds, are key to fertilising the top-quality New Zealand soil, he added.
"Northland has the highest number of seabird species in the world and seabirds are key fertilisers for the New Zealand soil and shore marine environment. There's a massive ecological system we're missing on the mainland New Zealand. When they can't survive here because of introduced predators, we lose a massive part of that nutrient cycle which affects fish stocks and humans."
Since 2002 when the trust began restoring habitat to its pre-European state on the pest-ridden Bream Head Scenic Reserve, there have been a number of conservation victories. They include self-reintroduction by native bird species such as kāka, the discovery of a new skink species and translocation of North Island robin and whitehead populations.
■ The grey-faced petrel is an-all dark oceanic seabird with a short but powerful, deeply hooked beak. At sea it is fast and graceful with a high-soaring, powerful flight on long, narrow wings. Grey-faced petrels breed around northern New Zealand, on islands as well as a few mainland headlands.
The birds begin breeding in the middle of winter, but many chicks don't fledge until the height of summer. The grey-faced petrel is sometimes referred to as the northern muttonbird, and some iwi still exercise their rights to harvest the petrel chicks between mid-November and mid-December each year.
Grey-faced petrels are making a comeback as many breeding islands have been cleared of pests.
