In the midst of the forest, one may experience a cacophony of sounds. The songs from a myriad of bird species, the rumbling of a chainsaw, and the piercing cry of a car alarm from a nearby road are all noises permeating the thick brush in Episode 6 of Life of Birds, Season 1. What David Attenborough discovers, however, is that all of these noises are coming from a single source: the lyrebird. Vocal mimicry, or rather the characteristic in which an individual learns and repeats a sound from another species or environment, is not uncommon across bird species, with around 20% of all species performing some form of mimicry [3]. Vocal mimicry is not limited to birds, suggesting that it is a case of convergent evolution. It has been heard occasionally in bottlenose dolphins, harbor seals, killer whales, orangutans, and African elephants, but these instances are rare compared to how often vocal mimicry is practiced in the avian class of vertebrates [3]. In Life of Birds, Attenborough acknowledges that, although a number of birds practice mimicry, the lyrebird is truly exceptional in this category, with its ability to imitate the calls of at least 20 different species, including man-made sounds such as cars and cameras. The vocal displays of the lyrebird are performed both as a mating ritual and as a form of territorial aggression, reaching peak occurrence during breeding season [1].
Many people believe the misconception that the fittest organisms in a population are the strongest, biggest, or the healthiest. This isn’t necessarily the case for the lyrebird. In lyrebird populations, males are subject to intense sexual selection in the form of elaborate tail feathers, synchronized dancing, and extremely intricate and complicated song compilations, none of which confer strength or health, but rather the ability to get genes to the next generation [4]. Female lyrebirds judge a potential mate on their mimetic accuracy, their repertoire size, and the complexity of their performance [2]. These preferences impose a series of costs and benefits to males. Benefits include increased access to food and reproductive advantages, whereas the costs entail increased risk of detection by predators and conflicting signal requirements [1].
Research has found that mimetic performance in terms of accuracy and repertoire size is superior in older males than juveniles, suggesting that there are developmental costs in attaining the adult song [2]. In the first 3-4 years of a male lyrebird’s existence, they focus on learning the vast array of noises that they want to include in their repertoire, and they then practice their mimic of these sounds in subsequent years to achieve peak accuracy [2]. Females can thus select for a mate on the basis that their accurate mimicry and vast repertoire, both which indicate a male’s superior quality and age.
Although lyrebirds appear to benefit from vocal mimicry in terms of reproduction, various other species benefit from this phenomenon for differing reasons. Vocal mimicry helps cuckoo birds parasitize other bird’s nests, helps spotted bowerbirds avoid predation, helps greater racket-tailed drongos to call for help, and helps parrots to form social bonds [3]. The evolution of vocal mimicry across a wide array of species continues to puzzle researchers and remains to be explained in future studies. Despite this, one can’t help but be impressed by the mimetic capacity of the superb lyrebird. With this in mind, next time you forget where you parked your car, don’t follow the alarm blindly into the forest or you might end up falling for the lyrebird’s irresistible charm.
by Ashley Rhodes
Life of Birds, Season 1, Episode 6, Signals and Songs, starting at approximately 37:35
References
- Dalziell AH and RD Magrath. 2012. Fooling the experts: accurate vocal mimicry in the song of the superb lyrebird, menura novaehollandiae. Animal Behaviour 83: 1401–1410.
- Zann R and E Dunstan. 2008. Mimetic song in superb lyrebirds: species mimicked and mimetic accuracy in different populations and age classes. Animal Behaviour 76: 1043–1054.
- Kelley LA and SD Healy. 2011. Vocal mimicry. Current Biology 21: R9–R10.
- Mulder RA and ML Hall. 2013. Animal behaviour: a song and dance about lyrebirds. Current Biology 23: R518–R519.
The Evolution of Planet Earth 