Listed as "nationally vulnerable", black petrels mate in New Zealand and winter near the Galapagos.

Young black petrel birds are migrating across the Pacific right now, to their second home around the Galapagos Islands and the western shores of South and Central America.

In May, scientists tagged 14 taiko​ fledglings with satellite tracking devices and have since been recording their movements across the ocean.

By the time this story is published Monday morning, some birds will have already arrived and others should appear over coming days.



The journey of more than 12,000 kilometres started in May and has already revealed a wealth of new data about the birds, says Nikki McArthur of Wildlife Management International Ltd. It's almost real-time science.



The birds (Procellaria parkinsoni) were laid in late 2017 in burrows high up on Aotea/Great Barrier Island in the Hauraki Gulf. They were raised by both parents and fed about every five days.



In May, the parents departed for their own migration to South America, leaving the fledglings on their own for about two weeks.

Wildlife Management International Satellite tracks of 14 black petrels migrating across the Pacific from late last week. Two transmitters stop working at the Xs.

"One night, [individuals] decide it's time to go," says McArthur.

"They find a handy tree … and climb it.

"It's quite bizarre to see a seabird climb a tree."



And then they launch themselves.



To this point, young black petrels have never flown.



Some immediately soar.



Some crash. After a while, they find another tree to climb and try again. Some launch from rocks.



But once airborne, they immediately start flying for the Galapagos. "They don't muck around," McArthur says.



He and colleagues at Southern Seabird Solutions Trust and the funder of this project, the Auckland Zoo Charitable Trust, had expected the young birds would remain in the Hauraki Gulf for a time, learning to fly and eat on their own.



Instead, their maiden flight is a 12,000km one. At least it was the for 14 tagged birds.



They flew independently but followed similar routes – pretty much due east. After passing Easter Island, they turned north for the islands off Ecuador.

Nikki McArthur, WMIL A young black petrel sits outside its burrow on Great Barrier Island.

As of late last week, 12 of the 14 transmitters were operating. The missing two may have fallen off, stopped working or the birds have died, McArthur says.

It's not known if the birds stop on the migration. The transmitting gear is not fine-enough scaled for that. But many migrating birds can sleep in flight.

Black petrels are "nationally vulnerable", with 10,000-15,000 animals left on the planet, McArthur says. In NZ, they are predated by pests and at sea they are bycatch to commercial and recreational fishers, the trust says.

Nikki McArthur, WMIL A satellite transmitter is attached to a black petrel. It's designed to fall off once the battery is dead, after about 12 weeks.

After arrival in the Galapagos and along the west coast of South America, the young birds will stay in the area for two or three years. They don't touch land the whole time.

There is no monitoring of bycatch during these years but it's thought to be heavy.

If they survive, they return to Great Barrier, and in smaller numbers to Little Barrier Island, where they again have to navigate foliage.

They basically crash through, says McArthur. "It's great to see ... on land they are clumsy."

After a year or two, the males evacuate burrows and call for females to join them. If she likes the look of things, they mate for life – producing one egg a year. It's believed they remain together for 20-25 years, a long time for birds.

Recreational fishers in the Hauraki Gulf are expected to Catch Fish Not Birds by avoiding behaviour likely to snare petrels and other seabirds. Read more: catchfishnotbirds.nz/avoid