Birds
Satin Bowerbird
Ptilonorhynchus violaceus · also called satin bowerbird
The satin bowerbird is an artist and a thief. The glossy blue-black male spends much of the year building and maintaining a woven avenue of sticks on the forest floor, obsessively collecting blue objects to arrange around it, painting its walls with chewed pulp, and raiding his neighbours’ collections when they aren’t looking.
Overview
Satin bowerbirds live in wet forest, rainforest edges, and adjacent woodland and gardens along the east coast of Australia. They are omnivores, eating mostly fruit but a lot of leaves in winter. Adult males are glossy blue-black with violet-blue eyes; females and young males are olive-green with scalloped underparts and look nearly identical for years.
The bower
The bower is not a nest. It is a display structure — two parallel walls of thousands of fine sticks, 20–30 cm tall, forming an avenue the male clears and tends at the same site for years. The female builds a separate plain nest in a tree and raises the young alone.
The blue collection
The male decorates the bower almost entirely with blue items — petals, parrot feathers, berries, snail shells, and, increasingly, blue human litter (bottle caps, pen lids, straws). Blue is rare in nature, so males compete, steal, and vandalise for it. Females judge males partly on the quality and quantity of the display.
Painting
The male chews plant matter, charcoal, or fruit into a paste and wipes it onto the bower’s inner walls, sometimes using a wad of bark as an applicator — a form of tool use. It is one of the few birds known to “paint.”
A long apprenticeship
Males take about seven years to gain full blue plumage. Green young males spend that time watching mature males, handling decorations, and building practice bowers that older males destroy. The oldest, most skilled males get most of the matings.
Status
The satin bowerbird is Least Concern, common in eastern Australian forests and tolerant of gardens.
Satin Bowerbird: common questions
What is a bower, and is it a nest?
It is not a nest and the female never lays eggs in it. A bower is a display arena built and tended by the male purely to attract mates. The satin bowerbird's bower is an "avenue" type — two parallel walls of thousands of carefully placed fine sticks, about 20 to 30 centimetres tall and a few centimetres apart, running north-south, with a cleared platform at each end. The male keeps the same bower site for many years, rebuilding and improving it each season. The actual nest is a separate, plain, shallow cup of twigs that the female builds by herself, usually high in a tree well away from the bower, and she raises the young alone.
Why is the satin bowerbird so fixated on blue?
It matches the male's own colour. An adult male satin bowerbird is glossy blue-black with striking violet-blue eyes, and his display objects reinforce that colour theme. Females assess males partly on the quality and quantity of the blue decorations, so males compete fiercely for a limited supply of blue things in the forest — blue is a genuinely rare colour in nature — and they steal each other's ornaments and even destroy rivals' bowers. The arrival of blue plastic in the environment has given them an abundant new source, and satin bowerbird bowers are now often decorated with bottle caps, pen lids, clothes pegs, straws, and bits of blue rope. This can be a hazard when nestlings are fed plastic fragments.
Do bowerbirds really paint?
Yes, in a limited sense. A male satin bowerbird takes plant material, charcoal, or crushed fruit into his bill, mixes it with saliva into a coloured paste, and daubs it onto the inner surfaces of the bower walls. Some individuals hold a small wad of fibrous bark in the bill and use it as an applicator or sponge, which counts as tool use. The "paint" is thought to affect how the bower looks under the dappled forest light and may carry a scent. Along with nest-decorating and stone-arranging, this is one of the clearest cases of an animal producing something for visual effect.
How do young males learn to build?
Slowly, and by watching. Male satin bowerbirds do not get their full adult blue plumage until around seven years old; before that they look almost exactly like females. During those years the green "psychedelic" young males spend a lot of time visiting the bowers of mature males, watching them display, handling the decorations, and building crude practice bowers of their own, which older males frequently tear apart. This long apprenticeship, combined with the male's long lifespan, means bower-building skill and the ability to hold a good site improve with age and experience, and the oldest, most experienced males get most of the matings.