Noted ornithologist John Gould wrote that, of all the birds he had ever met, the superb lyrebird was by far the shyest and most difficult to stalk. Albert's lyrebird is even more wary, and so has been little studied. Observations of a population of superb lyrebirds that have largely lost their fear of people (in Sherbrooke Forest, Victoria, Australia) have provided much of what is known of lyrebird behavior.

Lyrebirds are sedentary, though individuals may wander away from their defended territories outside the breeding season, or to drink and bathe, which they do daily. They are generally solitary, but occasionally two or more may be seen together, mainly outside the breeding season.

Female superb lyrebirds also maintain territories and defend them against other females. Their territories overlap male territories but do not coincide with them. The situation with female Albert's lyrebird territories is unknown.

The three major components of male lyrebird vocalization are: loud territorial songs; a display song consisting largely of mimicry and aimed at attracting females; and sequences of peculiar rhythmic sounds—the so-called "pilik song" of superb lyrebirds, and the "gronking song" of Albert's lyrebirds. Lyrebird vocalizations are culturally transmitted from generation to generation. All males in a local area use the same territorial song or songs, for example, although there is great regional variation.

Male Albert's lyrebirds weave mimicked sounds into a fixed sequence, forming a stereotyped song about 40-50 seconds long that may be repeated many times without a break. All males in a local area have the same sequential song, clearly demonstrating that it is culturally transmitted. Superb lyrebird mimicry appears to come in random order.

Lyrebirds are renowned for their powers of mimicry and it is widely held that they mimic mechanical sounds of human origin such as axe-blows and mill whistles. However, they rarely do so in the wild, and never as part of their breeding season song. Both species regularly produce with the voice the sounds of feathered wings. Albert's lyrebirds mimic the brush-tailed possum (Trichosurus vulpecula), a local nocturnal marsupial. Out of the breeding season, lyrebirds mimic a greater variety of sounds on an irregular basis.

Lyrebirds learn to sing by copying older lyrebirds. This applies to choice of mimicry as well as the lyrebirds' own sounds, though obviously hearing the mimicked species enables them to keep the mimicry accurate. When superb lyrebirds were introduced into Tasmania they retained in their mimicry calls of eastern whipbirds (Psophodes olivaceus) and of pilotbirds (Pycnoptilus floccosus), neither of which occur there. For several decades these calls remained clearly recognizable but were no longer recognizable in 2001.

During winter, the species mimicked by the lyrebirds are not themselves breeding and are mostly silent, and so potential confusion of auditory signals is avoided.

Both species have a variety of alarm and threat calls. The principal alarm call, a loud piercing shriek, is common to both species.

Lyrebirds fly poorly but can leap vertically 6 ft (2 m) or more. They prefer to gain height by leaping and climbing in the vegetation. This way, and flying as little as possible, they can gain the forest canopy for roosting.

At dawn a lyrebird waits until there is enough light on the forest floor before descending from the roost. Mature males often spend this time in intermittent song. Once on the ground in the breeding season, those males that are defending territories first spend up to two hours singing and displaying before commencing to forage.

0 0

Post a comment