http://www.nature.com/news/2004/040906/full/040906-1.html
Published online: 06 September 2004; | doi:10.1038/news040906-1
Parrots speak in tongues
Helen Pilcher
Ability to modify vowels underpins mimicry skills.
Ever wondered what makes parrots so good at mimicking human speech? It
turns out that the feathered impressionists use their tongues to create
vowel-like sounds, just as we 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.
Until now, many researchers thought that birds produced and modified
their song in the avian equivalent of the larynx, the syrinx, and that
the tongue played no role at all.
But parrots are known to 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' great talent for mimicry. Their results are published in Current
Biology1.
The team studied five feral monk parakeets (Myiopsitta monachus), 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.
Look who's talking
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.
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