A male builds an avenue of sticks with a court in front of it covered in stones, bones and shells, and arranges them by size: small ones near, large ones far. When researchers shuffled them, he restored the order within days. Why does it matter to him?
Because of where the female stands. From her viewing point inside the avenue, does the work: the angular sizes come out similar and the court looks flat and even. A distant object looks smaller, so putting the large ones far cancels that shrinking. The quality of the illusion predicted courtship success.
The male builds an avenue of sticks with a court in front of it covered in stones, bones and shells. It is not a nest but a stage: the female visits, assesses, and leaves to build a nest herself.
The arrangement is not random. He puts small objects near the avenue and large ones far from it. A distant object looks smaller, so from inside the avenue the sizes appear similar and the court looks flat and even.
The illusion works from one place only, and that is what makes it a test. The researchers photographed from there and measured size and distance, then went on to .
And when they shuffled the objects, the males restored the order within days, which rules out coincidence. The quality of the illusion predicted courtship success, although that association does not show it alone drove the female’s choice, and the males may be following simple rules of size and distance.
wat. A great bowerbird arranges objects by distance so that from the female’s viewpoint they all look nearly the same size.
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A bird can build a display that takes the viewer’s standpoint into account and systematically alters how objects appear.
How do we know?
The researchers photographed the courts from a female’s viewpoint, measured size and distance, disrupted the arrangement and followed the repair and the matings.
What is still unknown
The association with courtship success does not show the illusion alone drove the female’s choice, and the males may be following simple rules of size and distance.
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Where to next
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