Maybe you can make a celebrity impression or two bad ones, but can you mimic the cast of an entire movie at once? A superb male (Menura novaehollandiae) can, almost almost. During a courtship and even while mating, the birds pluck a similar feat, mimicking the calls and rhythmic noises of the wings of many species of birds at once.
The boys appear to be trying to recreate the specific ecological soundscape associated with the arrival of a predator, the researchers reported Feb. 25 in Current Biology. It is not yet clear why the boys do, but the discovery is the first time an individual bird has been observed simultaneously mimicking the sounds of several species of birds.
The strange acoustic imitation of multispecies flocks adds a layer of complexity to the werewolf's courtship song but is not seen in birds and raises questions about why their remarkable vocal mimicry skills evolved in the first place, including sounds like chainsaws and blinds.
The magnificent boys – originally from wooded parts of South East Australia – have a theatrical twist. Males have exceptionally long, showy tail feathers that sway extensively in elaborate mating dances (SN: 6/6/13). The musical accompaniment to the dance is predominantly a mixture of great hits from the songs of other bird species, whose role was studied by behavioral ecologist Anastasia Dalziell through audio and video recordings of the rituals.
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“When you listen to boys, you hear this very strong, very lyrical and dramatic delivery of mimicry of many Australian bird species,” says Dalziell, of Wollongong University in Australia. The shrill calls of kookaburras and parrots are common targets. "But when I started recording (lyrebirds) in detail and for long periods of time, I realized that from time to time they were doing something completely different."
The boys would move on to a shorter, quieter song, made up of fluttering noises and scattered tweets. Dalziell thought it looked like the mixed species of “mobbing flocks” he experienced in his fieldwork, where birds of prey detect a predator and group together in a strong, aggressive contingent trying to ward off the threat.
When Dalziell and his colleagues analyzed the acoustic signatures of the strange songs of the lilies and compared them with those of the effective mobbing bands, the similarities were striking. It was an impression accurate enough to deceive other birds as well. When the equipment reproduced the false noises of the parasite herd in the wild, the songbirds were attracted to the speakers to a degree similar to when the speakers reproduced the audio of a real mobbing flock. But the songbirds largely ignored the speakers when they played the typical mimicked melodies of the parasite.
“Mimicking the calls and beats of a group of small songbirds while docking predators is quite convincing to my human ears,” says Çağlar Akçay, a behavioral ecologist at Koç University in Istanbul who is not involved in this research. The findings, he said, are part of a "very great study of a very great animal."
While lilies can mimic a flock of mobbing, they may not do so to mimic the mobbing’s own intent, says Dominique Potvin, an ecologist at Sunshine Coast University in Queensland, Australia, who also did not participate in this research. Replicating mobbing calls, she says, could only be a difficult vocal feat to impress a partner.
Some clues as to why males sing these mobbing songs may come from their time. Video recordings reveal that males make calls right at the end of a courtship display and during mating. Dalziell says that herd mimicry is not about cutting a female, but deceiving her into believing that a predator is nearby. Such a tactic of this “master illusionist” can increase the chance of a successful mating by keeping the woman close.
At the end of the attempt to impress a woman with an elaborate song and dance, the male lily adds a remarkable bloom. His voice recreates the alarmed chirps and wingbeats of many birds of different species, a degree of mimicry never seen in birds.
Akçay is skeptical of this explanation. “Intuitively, it seems like it wouldn’t be exactly adaptive for a female to return to an area – to mate no less – if you get the impression that there’s a predator around,” she says.
The findings generate many new avenues for research, Dalziell notes. Determining whether females react to the simulated mobbing herd in a manner similar to the actual version may be a way to test the idea of deception.