In bushland along the east coast of Australia, male lyrebirds are putting on
a song and dance show all in the name of love.
By Abbie Thomas
If you're out bushwalking at this time of the year, don't be surprised if
you hear an especially piercing bird call, followed by a wave of more
familiar songs.
It's probably a lyrebird going through his repertoire, looking for love.
Winter is the time when female superb lyrebirds are fertile, and males sing
and dance their hearts out trying to attract a female mate.
For about six weeks, males sing intensely from dawn to dusk. You might hear
them at other times of the year, especially if it's raining, but winter is
when their vocal chords get a real workout.
The males build several mounds on the ground, and use these as a stage to
put on their extraordinary vocal and visual displays.
There are two species of lyrebird. The superb lyrebird is the most common
and widespread and is best known for the spectacular tail shaped like an
ancient Greek lyre (harp).
Albert's lyrebird is a smaller, less gaudy species, which is restricted to
just a few reserves in the far north-east corner of New South Wales and
south-east corner of Queensland.
Fast Facts
When: Lyrebirds call from June through to August
Where: There are two species of lyrebird. The superb lyrebird (Menura
novaehollandiae) live along the east coast of Australia from Stanthorpe in
Queensland to as far south as Melbourne. They have also been introduced into
Tasmania.
Albert's lyrebird (Menura alberti) is restricted to the extreme south-east
corner of Queensland and north-east tip of NSW.
Who's a pretty boy?
Anastasia Dalziell is just finishing her PhD on lyrebird communication at
the Australian National University. She was torn between pursuing music or
science, and so studying lyrebird song seemed the perfect solution.
"Studying lyrebirds is almost like the Holy Grail of songbirds, because they
have such a complex, intricate vocal display. It's overwhelming but really
fun," she says.
One song is good enough for most birds, but for lyrebirds, it's just a
start. They are choosy about which birds they imitate, and favourites
include the yellow-tailed black cockatoo, grey shrike-thrush, whipbirds and
rosellas.
"Kookaburras are also a great favourite - a lyrebird can do two kookaburras
calling at the same time."
So why go to all the trouble of impersonating multiple birds?
"Males sing during the time when the females are fertile, so singing is
related to gaining a mate," says Dalziell.
"But it also has a lot to do with the fact that male and female lyrebirds
have very different reproductive roles.
"The females do all the parental care - she builds the nest, cares for the
chick, and defends her own territory.
"That means she doesn't need the male to be a good father - all she needs is
for him to be beautiful and spectacular. The song is very flamboyant, very
loud, very complex, and over the top, and so the female is probably choosing
between males on the basis of how beautiful they are and how well they sing
and dance.
"When it comes down to it, he can put all his effort into his performance,
rather than being a dad."
Song secrets
While their impersonations are impressive, Dalziell wanted to test if
lyrebirds were good enough to fool other birds.
One of the birds that lyrebirds really like to imitate is the musical call
of the grey shrike-thrush. Dalziell made recordings of both real
shrike-thrushes, and also lyrebirds imitating shrike-thrushes. She played
the two recordings to a shrike-thrush to see how it would react (measured by
how close the shrike-thrush approached the speakers).
Dalziell says the shrike-thrush was totally fooled by the lyrebird
impersonation, showing as much interest in that recording as in a real
shrike-thrush call.
The astonishing ability of lyrebirds to mimic is partly explained by their
unusual throat structure.
Most songbirds, including the lyrebird, have a vocal organ called a syrinx,
located at the base of the trachea. Because it is located where the trachea
forks into the bronchii that lead to the lungs, birds can produce more than
one sound at the same time - one sound in each of the two bronchii.
Dalziell says the syrinx of the lyrebird is unlike most other songbirds,
with fewer muscles and probably greater flexibility, perhaps explaining why
lyrebirds can produce such a diverse range of sounds.
Fads, fashion and ferals
In the late 19th and early 20th century, the spectacular tail feathers of
lyrebirds were perched on many fashionable ladies' hats, and birds were
hunted in large numbers. Their ground-dwelling nature also made adults,
chicks and eggs vulnerable to introduced predators such as foxes and cats.
How then are superb lyrebirds still relatively widespread and easy to find
in the bush?
"They are real survivors," says Dalziell. Evolving alongside predators such
as quolls and Tasmanian devils, lyrebirds can take refuge in trees. They
also have excellent hearing and can let out a deafening scream, startling
even the boldest hunter.
Lyrebirds also cope well with bushfires. There are extraordinary stories,
says Dalziell, of someone fleeing a fire and taking refuge under a blanket
in a creek, only to find a lyrebird suddenly pop up under the blanket with
them. They have also been known to seek refuge from fire down wombat holes
and in caves.
One thing they may not survive, though, is climate change, says Dalziell.
Lyrebirds live in moist forests and rely on damp habitats to supply the
earthworms and other ground-dwelling invertebrates that make up most of
their diet.
"They can cope with many things, but I suspect they will have problems with
climate change: their habitat could dry out."
http://www.abc.net.au/science/articles/2011/08/04/3284076.htm
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