Lyrebird vocal diversity reduced in fragmented habitat

As the Albert’s lyrebirds’ Australian rainforest habitat shrinks, so does the number of sounds that the bird, a talented mimic, can produce – a degradation of lyrebird “culture” and a hidden loss of vocal diversity, researchers say.

The research was described in “Depleted Cultural Richness of an Avian Vocal Mimic in Fragmented Habitat,” published in the journal Diversity and Distribution by scientists affiliated with the Cornell Lab of Ornithology and Western Sydney University, the University of Wollongong and the Australian National University.

Across three years, during the lyrebird’s breeding season from May to July in Australia, the team gathered recordings of Albert’s lyrebirds from seven distinct populations.

A male Albert’s lyrebird doing its mating dance.

“Birds in smaller patches of habitat had smaller repertoires of mimicked sounds, mimicking fewer species and fewer vocalization types overall,” said lead author Fiona Backhouse. She led the research while at Western Sydney University and is now continuing the work as a postdoctoral researcher at the Cornell Lab. “The really interesting thing is that individuals who were mimicking fewer species seemed to partially compensate by mimicking more types of vocalizations for each species.”

Albert’s lyrebirds are slightly smaller than their more famous cousin, the superb lyrebird, but have a more brilliant rufous plumage to match the parasol-like tail feathers of the males. Both species are found only in Australia but there are fewer Albert’s lyrebirds – they are listed as Near Threatened.

When they sing, Albert’s lyrebirds mimic the same birds, in the same order, over and over, in a very structured format, up to about a dozen species. They most often mimic the satin bowerbird, crimson rosella and Australian king-parrot, throwing in the occasional vocal mimicry of bill clacking or wing beats. Albert’s lyrebirds also have their own unique sounds – the lyrical “whistle song” and a loud call they make during mating dances called “gronking.” But there are birds present that lyrebirds in some locations don’t mimic, though they do elsewhere, because there may not be enough other lyrebirds around to teach them.

Although they learn, in part, directly from the mimicked species, we were surprised by how much their repertoires were influenced by other lyrebirds,” Backhouse said. “Our study suggests that in these fragmented areas there are fewer lyrebirds, and that’s why their repertoire sizes are smaller. The lyrebirds don’t have lyrebird ‘tutors’ to learn from.”

This where the concept of “culture” comes in.

“In this context, the Albert’s lyrebird’s song is a cultural construct because the vocalizations are learned and each area has its unique variant of mimetic song,” Backhouse said. “There are many examples of non-human culture spanning a range of behaviors from vocal cultures to foraging techniques. One of the best examples of vocal culture is in humpback whales, where all males within a population share a unique song that is continually changing over time.

So, why do both lyrebird species mimic other birds if they already have their own songs?

Mimicry recording from the Mt. Jerusalem population in New South Wales, showing the species mimicked: From left, eastern yellow robin, satin bowerbird, crimson rosella, Australian logrunner, laughing kookaburra, Lewin’s honeyeater, Albert’s lyrebird.

“Vocal mimicry is fundamental to the acoustic ecology of lyrebirds: Female lyrebirds use it while defending their nests from predators, and the elaborate mimetic song of males is likely a way to show they are high quality in order to attract mates and discourage potential rivals,” said senior author Anastasia Dalziell of the University of Wollongong, also a Cornell Lab associate.

But Albert’s lyrebird faces an uncertain future. The species lost a third of its habitat to recent wildfires and Australia is getting hotter and dryer. Study authors hope their work offers a complementary way of assessing Albert’s lyrebird populations and habitat.

“The size of the repertoire can be a proxy for habitat size and quality,” Backhouse said. “Plus, it’s a quick, non-invasive way to monitor populations in the future.”

This research was funded by a National Science Foundation grant awarded to the Cornell Lab of Ornithology, by BirdLife Northern New South Wales, and involved the collaboration of scientists from the University of Western Sydney, the University of Wollongong, and The Australian National University.

Pat Leonard is a writer for the Cornell Lab of Ornithology.

Fiona Backhouse/Provided

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