Winter call of the lyrebirds
In bushland along the east coast of Australia, male lyrebirds are putting on a song and dance show all in the name of love.
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.
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."
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."
Published 04 August 2011