They show that, of the 30 most commonly observed seabirds off south-eastern Australia, 13 were in decline over the 2000-16 period, including the wandering albatross and the flesh-footed sheerwater. Five increased and the rest were steady.

Warming ocean temperatures driven by climate change are most likely playing a role in the decline by shifting cooler, more productive, waters south, according to the peer-reviewed research published in Biological Conservation.

"Seabirds are critically important organisms for maintaining the health of marine ecosystems," Mr Gorta said. "A lot of the groups that had a preference for colder-than-average water were declining."

The research was novel because it relied on citizen scientists to provide information on seabirds that would otherwise be costly and difficult to accumulate.

Since keen birders are active along Australia's coastline and many others around the world, the paper suggests there is much more information out there to be fished.

"It's an incredible wealth of data," Mr Gorta said. "We could potentially be finding answers for many questions related to seabird foraging ecology."

Richard Kingsford, professor of environmental science at UNSW and another of the report's authors, said pelagic citizen science was a valuable resource to track the environment.

"These people are consistently going out at the same time each year and doing the same thing," Professor Kingsford said, adding the data was particularly useful as most research into seabirds focused on their shore-based breeding colonies.

He noted that, while there were many pressures on seabirds from over-fishing of their food sources to plastic pollution, climate change that has caused the East Australian Current to strengthen and push tropical waters further south appears to be playing a role.

"There's certainly a decline going on [among common seabirds off south-eastern Australia] but there's probably a redistribution as well," Professor Kingsford said.

The paper noted that the results "need to be placed in the context of the highly mobile study organisms and the vast spatial scale of the ocean".

Even so, long-term citizen scientist observations "from an array of locations around the world, promise to provide valuable insights into seabird ecology".

Mr Gorta said the results published in the paper should encourage other amateur scientists to accumulate and report the information they gather.

"It's rewarding for people to know that not only is it fun, but it's also contributing to the conservation of the animals they love," he said.