For the Birds Radio Program: Birds in the News: Endangered Kiwis and Parrot Vocalizations (DD)
A coal mine may put endangered Great Spotted Kiwis in jeopardy in New Zealand, and ornithologists are manipulating the tongues of dead parrots as they pass air through the syrinx to see if they can produce vowel sounds.
Birds in the News: September 9, 2004
New Zealand’s Kiwis are our first story in this week’s “Birds in the News.” According to the September 9 edition of Bird Life International, “In the Waimangaroa Valley of New Zealand’s South Island, ornithologists and conservationists are campaigning against a decision to allow a state-owned company, SOE Solid Energy, to proceed with plans for a large opencast coal mine. The west coast Cypress mine would destroy hundreds of hectares of red tussock grasslands, wetlands, shrublands and beech forest – home to the Great Spotted Kiwi, which is classified as a vulnerable species. Tony Lockwood, Field Officer, Forest and Bird said, “At the same time as the government is spending millions of dollars a year through the Department of Conservation to halt the decline in New Zealand’s biodiversity, one of its own companies plans to open up a massive new opencast coal mine and destroy prime kiwi habitat.”
On the less depressing but perhaps more macabre front, up until now, many researchers thought that birds produced and modified their song in entirely in the syrinx—the sound production organ in birds, which is located where the trachea bifurcates into the bronchial tubes. The syrinx is far more complex than our larynx—so complex that most ornithologists assumed that it provided the entire sound production, and that the tongue played no role at all. But in the current issue of the journal Current Biology, researchers report that parrots use their tongues to create vowel-like sounds, just as we humans do.
In human speech, noise is produced in the larynx and can then be modified by the movement of the tongue in the mouth. This helps us to make complex vowel and consonant sounds. People have long noticed that parrots bob their fleshy tongues back and forth when they talk, so Gabriel Beckers from Leiden University in the Netherlands and colleagues decided to see whether these movements contribute to the birds’ ability to mimic human speech and a wide range of other sounds.
The team studied five feral monk parakeets which had been caught and killed as part of a government pest control program in Florida. In each bird, they replaced the syrinx with a tiny electronic speaker and then used a hook to move the tongue around as the amplifier played bursts of sound.
Tongue movements of less than a millimetre made a big difference to the quality of emerging vowel-like sounds, called formants, the team found. “It is larger than the difference between an ‘a’ and an ‘o’ in human speech,” says Beckers. Beckers thinks that the birds’ ability to manipulate their tongues to articulate vowel sounds probably underpins their talent as impersonators.
Parrots are likely to use these sounds in natural communication, says Irene Pepperberg from the Massachusetts Institute of Technology, who studies bird vocalizations. “Subtle differences in sound are very important to these birds,” she says.
Male songbirds, for example, tend to sing only at certain times of the year and for a specific reason: to attract females. But male and female parrots communicate all the time, says Pepperberg. They probably use formants and other vocalizations to convey complicated information, such as individual identity and predator threats.
The discovery “suggests that parrot communication may be more complex than we thought”, says Beckers.
Pepperberg has first-hand experience in this area. Her team has studied an African Grey parrot, called Alex, in the lab for 27 years. Alex can articulate sounds for objects, shapes, colours and materials, knows the concepts of same and different, and bosses around lab assistants in order to modify his environment.
Pepperberg claims that the ability to form vowel-like sounds is no accident. She says that it contributes to the richness of parrot ‘language’.
The recent study suggests that the ability to produce formants evolved at least twice, once in parrots and once in humans, says Beckers. Tongue articulation gives an extra dimension to vocal complexity, a phenomenon that must have proved useful to both species, though with the current political debate, perhaps evolution should have limited the experiment to the parrots.