A vagrant bird that looks a lot like a common seagull has set Australia's bird-watching community aflutter after the ninth ever sighting on Australian shores.

With news of the find spreading to interstate bird-watching groups, the struggling refinery town of Nhulunbuy in remote north-east Arnhem Land is expecting an influx of visiting birders or "twitchers".

The town 1000 kilometres from Darwin by road has been devastated by the closure of the alumina refinery last year.

The black-headed gull migrates between Europe and Asia but has been occasionally sighted further south.

On Tuesday last week ecologist Chris Wiley spotted the bird perched on an export conveyor belt, according to Amy Dewhurst, a member of the local bird-watching group.

On Monday the bird was seen a second time; veteran bird watcher Karen Rose photographed it on a local beach mixing with other gulls and terns.

"It's big news amongst the birding world," Ms Dewhurst said.

"This has stirred up all the wildlife enthusiasts and bird watchers alike down south. We're expecting to see a few visitors up here at the moment."

She said it looked very much like a common seagull.

"It's very hard to pick apart from a normal seagull apart from a black smudge on the back of the head," she said.

"Two significant white lines on the base of the wings makes it a little bit different."

She suggested the bird, which would usually be in Europe at this time of year, had been sucked into a storm and blown off course.

"Or he might be a little more adventurous than other birds," she said.

Ms Rose told 105.7 ABC Darwin this morning she had been standing on the beach looking for the bird since 6:00am.

"I've seen this bird in Denmark and in the UK," she said.

"It's a long way from home."

'Bird watchers very tempted to fly to Nhulunbuy'

The sighting would create "quite a bit of interest" among bird-watching groups, according to Sean Dooley, avid twitcher and editor of Australian Birdlife magazine.

He confirmed there were only eight recorded sightings of the bird ever in Australia, and this would be the ninth.

He said, however, that there may have been more unrecorded sightings; he saw a black-headed gull at Stokes Hill Wharf in Darwin in 2003.

"A bird seen less than 10 times in Australia does create a bit of interest," he said.

The town of Nhulunbuy on the Gove Peninsula 1000 kilometres by road from Darwin. ( Flickr: John Benwell )

"If it was the first time something like this seen in Australia we could expect to see several hundred [people] flying in to see it.

"When the first Chinese pond heron was seen in Darwin a few years ago dozens and dozens of twitchers came up from down south to check it out.

"A bird like the black-headed gull is very unusual and I'm sure a lot of people are thinking of heading up to look for it.

"Quite a number of people don't have this on their Australian list.

"They'd be very tempted to head up to Nhulunbuy."

About 900 different birds have been seen in Australia and of these 550 are breeding species, 150 regularly migrate to Australian shores, and the remaining 200 "blow in from time to time," he said.

"We're finding birds are turning up more and more.

"Whether that's due to habitat loss in Indonesia and they're moving across to find new places to live or whether the effects of global warming and changing weather patterns.

"Or there could be more bird watchers out there looking."

"There's definitely more rare vagrant birds turning up every year.

"The Australian list has increased phenomenally in the last 10 years. There have been about 60 additions."