Resident waders disappearing down-under
A recent study of Australia’s wetlands has revealed that 81% of resident wading birds have disappeared in just quarter of a century throughout the mostly inland habitats of eastern Australia. The paper, published in Biological Conservation, reported that agricultural extraction and inadequate water allocation may have caused the steep declines.
Scientists from the University of New South Wales undertook aerial surveys of wetlands in eastern Australia between 1983 and 2006. During the monitoring period all resident wading birds declined.
The steepest drop was observed in Banded Lapwing Vanellus tricolor whose population plummeted by 98%. Further significant falls were detected in Red-necked Avocet Recurvirostra novaehollandiae (-85%), Black-winged Stilt Himantopus himantopus (-80%), and Masked Lapwing Vanellus miles (-69%). Because resident birds don’t leave the country - unlike their migratory counter-parts - the researchers concluded that the declines were causes by changes within Australia.
Wetlands in arid Australia do not hold water every year. With many bird species relying upon wetland habitats for their food, the frequency of flooding is crucially important for their survival. Deluges of flood water – the life blood for breeding shorebirds - have been tamed by dams, levee banks and agricultural extraction. The researchers reported that wetland area declined at 40% of the most important sites. Floods are becoming increasingly rare.
“…the conclusion that these wetlands and the birds they support are in jeopardy is unmistakable” —Rob Clemens, Birds Australia's (BirdLife in Australia) Shorebirds 2020 Technical Manager
"Resident wetland-dependent birds have suffered dramatically from a reduction in rainfall in recent decades, and the reduced availability of water is under heavy demand from a range of user groups. Species such as Endangered Australasian Bittern Botaurus poiciloptilus are under severe threat from lack of suitable wetland habitat. Reform of the environmental water allocation process would alleviate the threat to such species", said Chris Tzaros, Birds Australia's (BirdLife in Australia) Conservation Manager.
The recent Biological Conservation study supports observations at coastal sites, but it is too early to infer that these declines in resident species are of the same magnitude throughout Australia's coastal wetlands. Birds Australia’s monitoring of coastal wetlands over the same time period suggests that some resident species - like Masked Lapwing - may be locally increasing. Population trends of resident waders on the coasts have yet to be fully assessed.
“The area covered in these surveys included over 33% of Australia, and the conclusion that these wetlands and the birds they support are in jeopardy is unmistakable”, warned Rob Clemens, Birds Australia's Shorebirds 2020 Technical Manager. Recent analysis conducted by Birds Australia, reported similarly alarming declines in migratory shorebirds. Curlew Sandpiper Calidris ferruginea and Far Eastern Curlew Numenius madagascariensis have fallen throughout southern Australia's coastal areas by 75% and 50% respectively over the last 25 years.
These new results will be assessed by BirdLife for their implications for the IUCN Red List classifications of the species concerned, which until now had been classified as Least Concern.