Increasingly worried: More than a quarter of a million waterbirds disappear from eastern Australia

Posted on Dec 19, 2024 at 09:12 PM

One of the biggest wildlife studies in the country found that drought had caused a 50% decline in waterbird numbers in eastern Australia since 2023.

Since 1983, the Eastern Australian waterbird aerial survey has been conducted annually. It is among the world's largest bird counts in terms of geographic coverage and one of the longest-running.

Drop in Bird Sightings: A Troublesome Trend

This year's 287,231 bird sightings were half of the 579,641 birds observed in 2023. Bird counts in the 2024 report were much lower than the long-term average, ranking as the 22nd highest in the survey's 42 years.

Prof. Richard Kingsford, the head of the University of New South Wales Centre for Ecosystem Science, who oversees the aerial surveys, expressed “wistful optimism” that there would be a sustained increase in bird populations after rainy years linked to the triple La Niña.

“In 2021 and 2022 there was a lot of flooding everywhere, and we know that there were a lot of birds breeding, but we just haven't seen the same sort of recovery,” he pointed out.

Covering 2.7 million square kilometres, or 11 times the size of the United Kingdom or one-third of the Australian continent, the survey monitors more than 70 species of waterbirds.

Moreover, it chronicles the distribution and breeding of waterbirds and the changes in the major rivers and wetlands of the Murray-Darling basin.

The four primary indicators of waterbird health—total numbers, species breeding numbers, and wetland area—were all in decline, continuing a trend of significant long-term declines.

Breeding bird abundance dropped to one of the lowest levels ever recorded, considerably below the long-term norm.

Key Habitats for Waterbirds

“The areas that these birds breed in and rely on are floodplain areas,” according to Kingsford. “So much of what we've done in building dams and diverting water has [affected] that flood water that's so critical for the wetlands. We are also increasingly worried about the effects of climate change, in terms of the drying out of the south-east of the continent.”

The climatic catastrophe hastens the drying up of wetlands. This year's total wetland area (122,283 hectares) was likewise much lower than the long-term average.

Kingsford underlined the need for the Murray-Darling Basin plan for river restoration, saying that although the pace of loss has slowed, it is not a full restoration. The strategy is helping to replenish river water, but the next assessment of the plan should take into account the significance of large floods for ecosystems and biodiversity.

The team conducted surveillance for potential outbreaks of avian influenza, the H5N1 strain that has devastated wild bird populations globally, but found no instances of mass mortality, a relief, according to Kingsford.

The Georgina-Diamantina River system in north-western Queensland's temporary wetlands was the area where the scientists identified the highest concentration of waterbirds. About 17%, or 50,000, of all the birds seen, were from Lakes Mumbleberry and Torquinnie.

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