“Alarm!” In the event of danger, a cacophony of the warning calls of various birds and hectic fluttering noises can be heard in the forest. This soundscape of fear is imitated by the magnificent male lyre-tail with his voice during courtship and mating, researchers report. It’s probably a nifty trick: the intimidating sound illusion likely causes the females to stand still, the scientists explain.
Like many bird men, the males of the magnificent lyre-tail (Menura novaehollandiae) impress the ladies of their hearts with song and dance. The show stars of the Australian forests are characterized by a special talent: In addition to the typical tone sequences, they also produce sound imitations of the voices of other birds and animals as well as environmental noises. Even the click of cameras and the rattle of chainsaws can reproduce with amazing accuracy what made them celebrities of the Australian bird world.
Quirky sound illusion
These bizarre birds have been the focus of researchers working with Anastasia Dalziell from Cornell University in Ithaca for some time. As they now report, they noticed an astonishing sound pattern in the course of investigations into the courtship behavior of the lyre tails: the males sometimes made a rather unpleasant roar instead of the typical metallic tone sequences. As it turned out, it is an imitation of the sound pattern that sounds in the habitat of the magnificent lyre tails when the local bird community is agitated by a threat.
As the researchers report, the feathered imitation artists imitate the mixture of alarm calls from various bird species and even round off the illusion with a vocal reproduction of the hectic fluttering noises. “Up to now, it was considered that there are three protagonists in imitation behavior in the animal kingdom: an imitator, an addressee and a model. But here we have an example of one individual – a male lyre-tail – mimicking an entire ecological scene that includes multiple individuals and multiple species that make sounds at the same time, ”says Dalziell.
As more precise observations have shown, the magnificent lyre-tails males apparently let the bizarre sound illusion sound specifically when the females want to evade their courtship behavior. Above all, however, the noise accompanies the copulation itself. “It finally became apparent that imitating the sonic panic reactions during copulation seems to be the rule with the beautiful lyre tails,” says Dalziell.
Sound: A splendid lyre-tailed male imitates the panic in the forest when there is danger. (Credit. Dalziell et al./Current Biology)
Sneaky delaying tactics
But why do the male birds fill their hearts with this terrifying din? It seems plausible that it is a delaying tactic – the females are, as it were, in a sensory trap, explain the scientists: The sound of the males makes the females behave calmly in order to avoid the attention of supposed predators. Dalziell explains: “It’s a bit as if they were telling the females: honey, it’s dangerous out there – stay here with me.”
Accordingly, the males apparently prevent the women from running away before they have had their say. And during copulation, they can then encourage the females to hold still for longer so that as many sperm as possible are transferred, the biologists suspect. As they emphasize, this contradicts the usual role of male sounds in the context of mating behavior in an interesting way: they are normally intended to ensnare the females and impress them positively. But in this case it is evidently a less “honorable” manipulation procedure.
Dalziell and her colleagues are now planning to take a closer look at the astonishing behavior: They want to examine the reactions of the females in detail in order to explain how the males benefit from the bizarre sound illusion. They also want to investigate another aspect that they noticed: During copulation, the male holds its wings over the head of the female. “Do you blindfold them, as it were, to prevent them noticing the deception?” Asks Dalziell.
Source: Cell Press, doi: Current Biology, doi: 10.1016 / j.cub.2021.02.003