Attenborough heads to Australia and New Guinea. Like the Birds of Paradise, Bowerbird females build their nests and raise their young alone so the male has all day to gather his treasures and create his bower. There seems to be a bowerbird rule: the more elaborate the bower the plainer the bird - the simpler the bower, the more vivid the plumage. David mischievously moves a leaf or a piece of lichen to see what the bird will do, then moves away. The bird flies back scoldingly and fussily returns his artistic display to its former perfection. Fascinating.