Australia has about 800 species of bird, ranging from the tiny 8 cm Weebill to the huge, flightless Emu. Many species will immediately seem familiar to visitors from the northern hemisphere - Australian wrens look and act much like northern hemisphere wrens and Australian robins seem to be close relatives of the northern hemisphere robins, but in fact the majority of Australian passerines are descended from the ancestors of the crow family, and t...
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Australia has about 800 species of bird, ranging from the tiny 8 cm Weebill to the huge, flightless Emu. Many species will immediately seem familiar to visitors from the northern hemisphere - Australian wrens look and act much like northern hemisphere wrens and Australian robins seem to be close relatives of the northern hemisphere robins, but in fact the majority of Australian passerines are descended from the ancestors of the crow family, and the close resemblance is misleading: the cause is not genetic relatedness but convergent evolution.
For example, almost any land habitat offers a niche for a small bird that specialises in finding small insects: the form best fitted to that task is one with long legs for agility and obstacle clearance, moderately-sized wings optimised for quick, short flight, and a large, upright tail for rapid changes of direction. In consequence, the unrelated birds that fill that niche in the Americas and in Australia look and act as though they are close...
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