Birdwatchers on the New South Wales mid coast have reported spotting record-breaking numbers of migratory and threatened waterbirds in an annual summer survey.

The Hunter Bird Observers Club recorded 3,773 individual waterbirds in one day in Port Stephens, north of Newcastle, in a survey undertaken by volunteers observing from a 'choreographed flotilla'.

Notably, the survey detected significant numbers of the critically endangered eastern curlew.

Alan Stuart, the club's field studies manager, said the highest numbers since 2010 were a welcome relief after years of declining sightings but that it was too early to be able to say why more birds were seen.

Mr Stuart said Port Stephens had always been an important site for the eastern curlew, a migratory shorebird that spent summer months on the estuaries and mangrove swampland along Australia's eastern coast.

"For as long as we can find records, Port Stephens has held at least 1 per cent of the total population, which makes it internationally significant," he said.

"In the past three years, the counts have dropped below 300, which is below the 1 per cent mark, but in the most recent count they're back up again.

"This count was just over 360, quite a step up over the past five or six years."

A new little tern colony has been found at Port Stephens, NSW. ( Supplied: Rob Palazzi )

Mr Stuart said the major threat to the eastern curlew had been the loss of feeding grounds on its migratory path between Australia and Siberia and it was possible the birds had found new flight routes.

"One of the big issues for all migratory shorebirds is a lot of the places they would normally stop over, like China and Korea where they stop and feed to renourish before they resume their journey," he said.

"Those places are under severe pressure from human populations with buildings and lots of disturbance, so they may have found a different way to get here."

He said there were good things happening at government and volunteer levels to address the problem, a sentiment supported by conservationists.

The Hunter Bird Observers Club was also celebrating healthy numbers of the Australian pied oystercatcher, another shorebird with an internationally significant population in the Port Stephens harbour.

A pair of pied oystercatchers off the mid NSW coast. ( Supplied: Gary Tong )

Mr Stuart said when the club began its annual summer surveys in 2004, no-one had known how many pied oystercatchers were in the area, and it was a "huge surprise" to find about 100.

He said the bird was listed as endangered in New South Wales, and the disturbance of its coastal habitat was contributing to a general decline in numbers.

During the one-day survey, Mr Stuart came across a new colony of little terns on an island in the harbour where they had never been seen before.

The migratory bird flies from eastern Asia to most parts of Australia in spring and summer, but is also considered endangered.

Mr Stuart said he saw several 'runners' — chicks that had not learned to fly yet who run and hide from danger.

Two little terns on mudflats in Port Stephens, north of Newcastle. ( Supplied: Steve Merrett )

He believed the little tern colony may have moved from a site nearby to the more peaceful island.

"They're endangered in NSW and really suffer because of an inability to successfully breed," he said.

"They breed on beaches or sand dunes and that gets a lot of disturbance from four-wheel drive traffic and people with dogs, as well as weather events.

"So it's always good news when they do manage to raise some chicks."

Birdwatching: the original 'citizen science'

Mr Stuart said while the annual survey was supported by NSW Government bodies, National Parks and Wildlife and the Office of Environment and Heritage, it could not have been done without the dozens of volunteers who took part each year.

"Citizen science is vital," he said.

"You can't do bird population studies without lots of people to pitch in and help."

The growing citizen science movement reaches across all kinds of scientific research, from plants and animals to space.

Erin Rogers, the chair of the Australian Citizen Science Association, said it could provide meaningful data to help form decision-making, while also engaging the general public in science.

"Perhaps they don't have a PhD but they're actually incredibly skilled people," Dr Rogers said.

"Birders are the classic example, where many people can be better than the professionals."

Alan Stuart and fellow Hunter Bird Observers Club member John Cockerell. ( Supplied: Alan Stuart )

Professor Justin Marshall, the chief investigator at Coral Watch, said birdwatching was the oldest form of citizen science, originating in the United States.

He said in ornithology, as in marine biology, getting the public to help collect data was highly efficient, as it flowed directly from the field to the spreadsheet or laboratory.

But Professor Marshall said citizen science also flowed in the other direction.

"It's a two-way conversation that encourages the public to understand a problem," he said.

"Involving someone helps them make their own decisions and leads to behaviour change."

Alan Stuart said he hoped that the positive data collected this year by amateur birdwatchers at Port Stephens would now boost the case for funding to find out more about the birds of the area.