A rare, endangered New Zealand bird has been seen in Australia for the first time.
Birdwatchers are still marvelling at the unexpected sighting of a black-fronted tern, which was seen in late June in Newcastle, in the New South Wales Hunter region.
The NSW Woodland Bird Program manager at Birdlife Australia, Mick Roderick, said it was an incredible discovery because the tern was endemic to New Zealand.
"It's a mind-blowing sighting that we're still trying to make sense of," he said.
"I've also been in touch with New Zealand researchers, and they're all very excited about it too.
"This is a bird nobody expected to see in Australia. It's a New Zealand breeding endemic. It has taken everyone by surprise.
"Until now, every single black-fronted tern has only been found in New Zealand, so this is a very exciting record for Australia."
Roderick said the sighting was also significant due to the relatively low number of black-fronted terns.
"This is a bird with a total population of only 5000. This is an endangered and rare bird," he said.
'We were pretty thrilled'
The black-fronted tern was spotted by Hunter Bird Observers Club member Michael Kearns during wild weather at Fort Scratchley.
Roderick - who is also a member of the club - said the sighting was quickly verified.
"Michael Kearns was out in the rain and the southerly winds, and he was looking for seabirds - albatrosses and things.
"As he was doing that, this unusual tern flew across," Roderick said.
"It immediately twigged with him that it was unusual.
"He put a message out on our local Hunter chat group and someone else happened to be up there at the same time.
"The bird was seen very briefly but photographed very well, so there's no doubt about the identification."
It was fellow Hunter Bird Observers Club member Jon Spicer-Bell who also saw and photographed the bird.
"We were both pretty thrilled, thinking it was an Arctic tern," he said.
"The realisation it was actually a black-fronted tern was incredible, knowing how significant the observation is to the birding community."
How did rare tern end up in Australia?
One theory is that the bird might have been blown off course by strong southerly winds.
"Black-fronted terns breed on the South Island of New Zealand and, after they breed, they disperse, mostly to the coast of the South Island, but some birds do cross over to the North Island," Roderick said.
"We do know there were a reasonable number that actually crossed to the North Island this year.
"So perhaps one of those birds that made its way across to the North Island and just got picked up in the big southerly that was blowing at the time and found its way to the east coast of Australia, in Newcastle."
New Zealand-based ornithologist Mike Bell has worked on black-fronted tern conservation programs for nearly 20 years.
He agreed it was likely it was a bird that had been migrating across Cook Strait to the North Island.
"It's a pretty huge sea crossing for this species, one which usually stays within sight of land," he said.
"It wouldn't be one that I would have expected in Australia, with its inshore behaviour, but great to know it can survive the deep-sea crossing."
Bell said New Zealand conservationists were working hard to protect the species.
"The birds are in serious decline. The threats on the braided rivers are many and, to be honest, we haven't 100 percent cracked how to save them yet," he said.
"We are only just starting to get the formula right, and making a wee bit of headway in a couple of spots."
Will endangered bird make its way home?
The black-fronted tern has not been seen in Australia again since the initial sighting.
Roderick said hopeful birdwatchers had travelled to Newcastle.
"There have been searches since. A lot of people have come up from many places to try [to] find this one bird, but it hasn't been seen since," he said.
Roderick said it was hoped the tern would eventually find its way back to New Zealand.
"We really don't know what will happen to the bird. Normally, with vagrant birds, they spend time at the place they've arrived and then they disappear," he said.
"It's an absolute mystery what this bird will do next.
"Let's hope instinct will kick in and it decides to cross the Tasman Sea and head back to New Zealand."