Gisella Kaplan, a professor of Animal Behaviour at the University of New England, said the migration pattern of the "brightest bird in the world", originally from inland Australia, was intriguing.

She said the highly-evolved birds formed loving, life-long partnerships with each other.

"They are charming, family loving, solidly cooperative, highly intelligent and long-lived.

"They, and our other cockatoos, are about the pinnacle in bird evolution."

They also loved to play, according to Birdlife Australia's Sean Dooley.

"They get their fill quickly in the day from their food and have a lot of time for working out their social hierarchy and play and getting up to mischief," he said.

And perhaps it is that tendency for mischief which has many neighbourhoods unhappy with the corellas moving in.

Once an inland bird, the corellas may be smart and playful, but they can also be destructive.

There have been calls for them to be culled in one area in South Australia and a priest on Western Australia's mid-west coast suggested birth control for the birds to stop them damaging an historically-significant cathedral.

Mr Dooley said it was a problem across many areas.

"Where they have expanded into [an area] they are occurring in super abundance," he said.

"It's actually creating a lot of issues for farmers and people in urban areas and also the ecology of areas.

"We know for a fact in some areas some less aggressive parrots are being out muscled by the corellas, including a species of black cockatoo, regent parrots in South Australia, rosellas and smaller parrots."

Why have some corellas made a sea change?

Mr Dooley said corellas had an ability to adapt to different food sources and landscapes and because the birds had expanded their range over the years, they often headed to coastal and urban areas in search of habitat, food and water.

"We do know especially with the little corellas, and the long-billed corellas, that they are expanding their range and numbers.

"The corellas have gone into areas that corellas have never set foot before, like the galahs before them.

"Galahs were essentially an inland bird, as was the little corella, and galahs reached the coast earlier in places like Sydney and Adelaide in the '50s and '60s, but the corellas were a bit slower to do it.

"Once the corellas have arrived on the coast, which has generally been from the late '90s onwards, we think in some ways associated with the millennium drought which pushed them out of their normal range, they have just boomed in numbers and never left."

Pet corellas contribute to 'super flocks'

Mr Dooley said escaped pet corellas had compounded the issue.

"We also think there may be some mixing of escaped pet birds ... so we find in areas where corellas never existed there's now feral flocks of corellas and in some places they seem to be mingling with the refugees from the inland, so we get these 'super flocks' of corellas," he said.

Professor Kaplan from the University of New England said the assumption that flocks of corellas equated to an abundance of the birds was misleading.

"Corellas prefer to move in small flocks of 20 or 30, but what we have seen in the last [few] years in Western Australia and South Australia and occasionally in Sydney, is huge flocks of thousands, but that doesn't necessarily mean that their numbers have increased," she said.

"It can mean that they have all fled from somewhere and flocked together ... in most cases, it happens when there is a dire shortage of food and water or the heat gets so bad they have to flee the inland.

"We need to help them survive because in some cases it could be that the huge flock may be the sum total of all the birds that exist in that state and that entire huge region.

What are the solutions?

Professor Kaplan said it was wise to look beyond culling corellas. "They bond and have a partnership very much like a marriage for life.

"Blindly shooting or destroying them can mean years of loving relationships broken and really doing damage to the species as a whole.

"There can be thoughts of doing something constructive, setting up sanctuary areas, where the corellas can live and roost and start planting vegetation and creating corridors for them.

She said the introduction of controlled birds of prey could be beneficial.

"In England and the United States, they commission licensed falconers at military sites and airports, and if there are sudden flocks of birds interfering with exercises or flight paths, they get a bird of prey in and it disperses the birds quickly," she said.

In South Australia, the Department for Environment and Water said it was leading the co-design of a South Australian Little Corella Management Strategy, due for release in coming months, to "strategically and humanely deal with little corella impacts for the long-term".