Friday, 21 February 2020

WHITIANGA WEATHER

Fascinating research at Ohinau Island

On his way to Ohinau Island, Patrick Crowe of Wildlife International Limited (WMIL) popped into The Informer’s office on Monday this week to talk about the flesh-footed shearwater research WMIL is undertaking on the island.

“There’s a large shearwater breeding colony on Ohinau, probably about 4,000 breeding pairs,” says Patrick. “They make a lot of noise. We’re an ecological consultancy and have been doing research on the island for several years now. We’re contracted by the Department of Conservation and our work is funded through a commercial fishing levy.

“Flesh-footed shearwaters are a high-risk seabird species form a conservation perspective and we don’t know much about them. We normally make two trips per year to Ohinau, one in January when the breeding pairs are incubating their eggs and one in May when the chicks flee the nest. This year we’re making three trips as we’re tracking the adult birds’ foraging habits during incubation and when the chicks have hatched.”

Last month, Patrick and a colleague fitted small tracking devices, weighing only 15g each, to 26 birds. This time around they plan to fit devices to at least 25 birds. They plan to be on the island for 17 days. “There’s no fresh water on Ohinau,” says Patrick. “We have to take all our water and food with us. The Mercury Bay area is very dry at the moment and I don’t expect things to be any better on the island.”

Shearwaters always breed with the same partner. A pair produce only one egg per year. “Between 50 and 60 per cent of the eggs on Ohinau will hatch successfully,” says Patrick. “We should see more than 2,000 chicks when we arrive at the island. All indications are that flesh-footed shearwaters live a long life, possibly up to 50 years, so it’s quite possible for a breeding pair to produce 30 or more chicks during the course of their lives.”

WMIL’s research to date has revealed that the male partner of a breeding pair will arrive at Ohinau during September/October every year and get the pair’s burrow ready for the female’s arrival. “It’s quite spectacular to watch,” says Patrick. “The male will almost ‘crash land’ next to their burrow, the same burrow every time.”

A month or so later, the female partner will join the male and an egg is produced approximately December every year. “This is basically impossible to research, but the breeding pair mate at sea, before the male’s arrival at Ohinau,” says Patrick. “Once the egg has been produced, the male and female partners take turns to incubate the egg. While the one partner stays at the burrow, the other will forage for up to two weeks to build up condition for when it’s their turn to incubate the egg.

“Our tracking in January gave us an insight into the distances the adult birds travel to forage during the incubation period. One of the birds flew more than 8,000km in approximately two weeks.”

Once a chick has hatched in late January/early February, one of the partners of a breeding pair will always stay with their chick, while the other one goes out foraging for food. Patrick says these trips are much shorter than during the incubation period. “An adult bird will go out for a short trip of one to three days to find food for the chick and then stay behind to feed and look after the chick, while the other partner goes out to look for food,” he says. “That will be followed by a longer trip of up to seven days with the foraging bird finding food for itself too.

“We hope the birds we fit tracking devices to during this visit to Ohinau will give us some good insight into where the shearwaters forage when they have a chick at their burrow they have to feed.”

Breeding pairs will stop feeding their chicks during April/May, upon which they will leave Ohinau and fly to the coast of Japan where they will remain until it’s time to return to the island to produce another egg.

“The research we do on Ohinau Island is fascinating,” says Patrick. “There’s so much more we have to learn. In the end, we hope what we do will contribute to flesh-footed shearwaters not only surviving, but thriving as a seabird species.” 

Pictured: Patrick Crowe of Wildlife Management International Limited with one of the tracking devices they plan to fit to at least 25 adult flesh-footed shearwaters at Ohinau Island this month.

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The Mercury Bay Informer is a highly popular community newspaper, based in Whitianga. The paper is distributed throughout the Coromandel Peninsula, coast to coast from Thames to north of Colville.