A fluke sighting of a deformed seagull during a lunchbreak has led to Australia's only record of a wild bird with multiple feet or limbs.

Key points: Only two instances of wild birds with extra limbs had been recorded globally before a recent sighting in Tasmania

Only two instances of wild birds with extra limbs had been recorded globally before a recent sighting in Tasmania Dr Eric Woehler, a veteran ornithologist, has had his sighting of a three-legged gull officially recognised in a science journal

Dr Eric Woehler, a veteran ornithologist, has had his sighting of a three-legged gull officially recognised in a science journal The bird was behaving normally, Dr Woehler said, and did not seem to have been shunned by the flock for its gratuitous endowment

Ornithologist Eric Woehler was taking a break from surveying birds with a student on the waterfront at Triabunna, on Tasmania's east coast, when he noticed a silver gull with a strange leg.

He managed to photograph the bird, but it wasn't until he examined the photos later that he realised how significant the sighting was.

"We saw there was a clear abnormality in the leg of this particular silver gull," Dr Woehler said.

"We believe this is the first record of this abnormal leg formation in a wild bird in Australia.

"It's just remarkable."

The bird had a third foot, as well as the bones and tissue of a third leg.

After scouring journals and contacting colleagues, Dr Woehler found no record of the abnormality in Australia, and only two other cases in the world.

The seagull appeared to have part of a third leg as well as a third foot. ( Supplied: Dr Eric Woehler )

'Remarkably rare'

The Marine Ornithology journal has this week accepted Dr Woehler's report on the bird, which he spotted last month.

"These abnormal developments in seabirds are remarkably rare," Dr Woehler said.

"We need to document them to get a better sense of the true extent in the population.

"By talking with various other gull researchers around Australia … the fact that none of us had ever seen this abnormality before clearly reinforced that it was a very rare phenomenon."

He said extra limbs and digits were more common in the mammal world, as well as in chickens due to the species being inbred.

"These are wild birds, and it's something we just don't see," he said.

Dr Woehler has been surveying seabirds for decades, but has never come across a wild bird with a third leg or foot before. ( Supplied: Dr Eric Woehler/BirdLife Tasmania )

Bird behaviour normal

Dr Woehler said the bird was at least four years old, and while it was unlikely that it could put all its weight on the deformed leg, it was healthy and behaved normally.

"It hasn't had an impact on the ability of the bird to feed and survive in the wild," he said.

"It was part of a large flock of birds hanging around a port facility and doing what silver gulls do best — looking for food scraps and offerings.

"There was no sense the abnormal leg was seen by the other gulls as a weakness that could be attacked."

He said he wouldn't be able to try and find the bird again due to COVID-19 restrictions, and that in any case it would likely be an impossible task, given there are about 16,000 silver gulls in south-east Tasmania.

If members of the public see the bird, Dr Woehler says he'd like to hear about it.

There are about 16,000 silver gulls in south-east Tasmania. ( Supplied: Dr Eric Woehler )

A genetic abnormality

Of the two cases of extra limbs on birds in North America, one was said to be caused by a genetic deformity and the other was linked to harmful chemicals in the environment.

"We believe this case is likely to be a simple genetic abnormality that occurred in the egg when the chick was developing," Dr Woehler said.

While birds with three legs are all but unheard of, Dr Woehler says spotting one-legged seagulls is common.

"Most of the losses of lower limbs in gulls are probably due to entanglement in plastic and fishing lines," he said.

"The lines wrap around the feet or legs resulting in a restriction of blood flow, and you get gangrene and the foot or leg drops off because the tissue is dead.