Bird researchers are relieved to find that the majority of the endangered purple-crowned fairywrens (Malurus coronatus), a small, social bird found in dense Australian vegetation, survived one of the region’s worst flooding in January and were still breeding.
Western Australia entered a state of emergency when ex-Tropical Cyclone Ellie inundated the Kimberley region with unprecedented flooding, washing away a major bridge and isolating communities for weeks after the heavy rainfall.
In the months after, communities, researchers, and conservationists returned to the sanctuary to conduct damage assessments, repair road access, and restore electricity and water facilities.
A supplied image obtained on Wednesday, Jan. 4, 2023, of floodwaters in the Kimberley region of Western Australia. A remote Western Australian town surrounded by a 100-year flood has become a refuge for hundreds of people evacuated from outlying communities. (Andrea Myers/AAP)
“Although the fairywrens have taken a bit of a hit from the flood, they are doing well considering,” said Monash University PhD student Ian Hoppe.
The purple-crowned fairywren population was estimated to be at 242 in May 2023, a slight fall from 256 in Nov. 2022.
Sadly, the birds are threatened by the impact of increased flood frequency, feral herbivores, wildfires, and habitat degradation by over-grazing, according to the 2020 Action Plan for Australian Birds.
“About three-quarters (74 percent) of the adult birds that were present in a census of the population at the end of 2022, just before the floods, are still alive now,” Hoppe said.
“This survival rate is lower than we usually observe over the November to May time period; however, it is not as devastating as we might have expected from such an extreme flood event.”
Much to the relief of the researchers, 24 out of the 67 breeding groups in the population also had fledglings accompanying the adult birds, despite all nests being washed away in the flood.
While the usual breeding season is December to April, multiple wrens were also found to be breeding one month later in May, with adults feeding young chicks in the nests, incubating eggs, and starting to build new nests.
“Although surprising to see that the birds are still breeding this late in the season, we’re not entirely shocked,” Postdoctoral Research Fellow Niki Teunissen from Monash University explained.
“We have noticed that in wet years birds often keep breeding for longer. Presumably, this is partly because in very wet years, floods frequently wash away nests, and birds don’t breed successfully until later in the season,” she said.
“We are confident that the population will bounce back.”
Meanwhile, Australian researchers have discovered that Australian birds teach their unhatched chicks a unique tune that allows the parents to distinguish their babies from parasitic cuckoos when their babies are begging for food.
The “incubation calls” include a series of two tones that are repeated.
“Parents and others attending the nestlings will only feed them if their begging calls contain the learned password,” said study co-author Sonia Kleindorfer at Australia’s Flinders University.
The researchers noticed the mothers calling to their eggs and found that this single-note call varies between nests.
By placing eggs in different nests, the scientists discovered that the hatchlings’ calls matched those of their foster mother rather than their biological mother, demonstrating prenatal learning.