The study revealed sightings of almost half the 30 most abundant seabirds - including the wandering albatross and flesh-footed shearwater - had fallen in the region over a 17-year period between 2000 and 2016.

Seabirds are critical in maintaining healthy marine ecosystems, acting as predators that feed on a range of prey.

"Our findings are worrying, not just because 13 of our more common species are declining, but because we don't know for sure what is driving these declines," lead author and University of NSW honours student Simon Gorta said in a statement on Monday.

Researchers at the UNSW Centre for Ecosystem Science suggest that warming ocean temperatures are likely contributing to the trend.

The east Australian current has strengthened off the country's southeast, which has led to warmer and less productive waters in the region. That is potentially driving birds to hunt elsewhere, Mr Gorta said.

"We can predict that as surface temperatures increase with climate change, we will be seeing fewer species that prefer cooler-than-average surface temperatures," he said.

The research, published in the international scientific journal Biological Conservation, was based on data collected by birdwatchers who go out to sea almost monthly.

Australian Associated Press