USD Biologist Studies How Rainfall Influences Reproduction in Australia's Chestnut-Crowned Babbler
Rainfall is scant and unpredictable in the arid environment of inland southeastern Australia. This characteristic also makes the location a prime place to study how climate factors influence reproduction in animal species such as the chestnut-crowned babbler, a bird endemic to the region.
Liebl, an associate professor in the Department of Biology, recently published a research article on the topic in a special issue of the journal Integrative and Comparative Biology. The article, “Clutch Size, but Not Egg Volume, Increases with Rainfall in Arid-Dwelling Bird,” describes the tradeoffs made by female birds of the species when responding to changes in rainfall and temperature.
“These babblers live in the Australian Outback, which is a super awful environment. Really nothing should live out there,” Liebl said.
Unlike other arid locations, where rainfall is more predictable, the annual amount of rain in the Australian Outback varies considerably, Liebl said. Adequate precipitation provides a breeding ground for the insects that make up the diet for babbler adults and chicks.
While birds in other environments with more stable weather patterns have evolved to use cues such as hours of daylight to start their breeding cycle, babblers in the Outback can’t rely on such factors.
“For a lot of birds, there is a reproductive season,” Liebl said. “They either breed or don’t breed, but they have a window. With these babblers, they must be more responsive.”
Researchers are not certain how the birds know when to start breeding, Liebl said, but they hypothesize that some environmental signal, such as certain amount of precipitation, triggers the babblers’ hormones to ramp up and for males and female to begin breeding.
“It’s costly for them because they have to be constantly waiting and surveying the environment,” she said.
Liebl and her research team examined data from 14 breeding seasons and found that clutch size – the number of eggs laid in a single nesting period – increased with higher rainfall. Egg size, on the other hand, decreased as clutch size increased.
These types of reproductive tradeoffs are increasingly interesting to scientists as climate change creates less predictable environments and extreme weather events.
“Looking within a species, it’s really interesting to think about,” Liebl said. “Do they put more resources into each animal and make them stronger or will they just make more of them? In this species, they are making more of them.”
Liebl’s co-authors on the research article are from the University of Exeter and the University of Cambridge in the United Kingdom, Macquarie University in Australia and Te Pūkenga in New Zealand.
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