Bowerbirds – nature’s “players”
Obsession with treasure to the point of insanity, piracy and dirty tactics… It is this attitude that, without a shadow of doubt makes bowerbirds my favourite group of birds.
Male bowerbirds go to extreme lengths to attract females, unlike anything you would ever see in other groups of bird – they build a bower. So what exactly is a bower? It’s a structure built by the bird specifically to attract females, nothing else. Many observers can confuse these wondrous structures with a sort of a nest, or even a sleeping shelter (in fact several groups of Australian birds do make such things). Male bowerbirds have no need to make a nest, they play absolutely no part in child-rearing to the point of having children with as many females as physically possible. So, they set up a territory and get to work building their Magnum opus.
Much like a suburban human rev-head with a customized car, or Hugh Heffner’s mansion the bowerbird’s bower is an extension of himself, an artistic statement to show off who he is, and of course reel the ladies in.
The first type of bower exhibited by the family is, well none at all. Catbirds are found in eastern Australia and the mountains of New Guinea. They are typically green and fairly nondescript. They have been observed with very primitive ‘bowers’ at times, but they are merely a collection of twigs and objects that seem to be carelessly dropped in a spot – they don’t seem to require one at all. Catbirds got their name from the cat-like scream they let out in the dense forests. The species shown is a spotted catbird from northeastern Australia.
Slightly, but barely more advanced is the arena constructed by the tooth-billed bowerbird (Scenopoeetes dentirostris). Named for the tooth-like structures in its beak, this bowerbird is a dull green-brown with a white chest marked with black vertical dashes. Males clear out a section of forest floor, stripping it right down to bare dirt and set out into the forest to collect green leaves. He carefully selects the ones that please his eye the most and place them about on his ‘stage’ and perches on a horizontal branch above it to sing. There is a curious relationship between bowerbird’s plumage and their call. Species with more dull plumage tend to be better songsters. The tooth-billed bowerbird is no exception. Males try to out-sing nearby rivals by imitating other sounds they hear. And they are very good at it, almost as good as the famous lyrebirds of further south.
The most common form of bower in Australia is that of the avenue variety. Around six of the ten Australian bowerbird species make this type. It is simply made of two parallel walls, kind of like a skateboarder’s half-pipe, decorated with all sorts of treasures. What exactly constitutes treasure is up to the individual male bowerbird. Male satin bowerbirds (Ptilonorhynchus violaceus) are famous for collecting blue objects, in fact practically anything blue will do just fine. Feathers, clothes pegs (many clothes have been found in the dirt under many washing lines where these birds live!) jewelery, bottle-tops, berries, drinking straws and so on. In fact, he will even chew up blue berries and paint the walls of his bower with the paste!
Less obsessed with any one colour are the four species of spotted bowerbird (Chlamydera species), two of which specialize in arid and semi arid parts of Australia. Also building the avenue bower, they are more flexible in colour choice and will use mostly white objects which are more common in the dry zones such as sun bleached bones, quartz stones and mollusc shells. In suburban areas, they will also make use of other colours, in fact the male great bowerbirds (Chlamydera nuchalis) seem to experiment with themes, some individuals going for green, others trying out white décor, and some trying out a layered approach with several colours.
An even more drastic bower is built by the golden bowerbird (Prionodura newtoniana).One of the smaller species, its bower is huge, the one pictured is almost the size of a queen sized mattress. Living only in high altitude forests, it is the only Australian bowerbird to build the ‘maypole’ style which is more of a fad with the species of New Guinea. A male simply selects two saplings and goes about gathering twigs, stacking them around them to build a big ‘U’ shaped bower. Normally there is a fallen branch between them which acts as further support. In the middle of the bower he places pale moss and flowers he has gathered from around the area in a very well arranged bouquet.
Male bowerbirds are obsessed with their creations, never straying far from them and spending much of their day finely adjusting it, moving a twig here and there, turning over objects to show off the best angle, stepping back to admire the treasure display and modifying it with more treasure. If a male does head off to get some food or more baubles for his bower, rival males will often sneak in to steal treasure and sabotage the bower. The theft of objects does explain the appearance of rainforest snail shells on the floodplains many kilometers away, the same shell must have been acquired by several males from their rivals and passed about the local bowers.
The reason male bowerbirds are so exact with their bowers is because the females are so incredibly choosy. Females will tour the area and look at bower after bower until one impresses her more than the others. If she comes in for a closer look, the male goes into a ritual dance, jumping about and making all sorts of other-worldly noises. If he has a crest he will raise it to show off, often picking up treasures to show to the female individually. If she is happy, she will mate with that male on the spot and likely never see him again – that is until she feels like raising another brood. The nest is built in a tree much like the more ‘standard’ bird nest and the female bowerbird will raise the young unassisted. Bowerbirds flourish in Australia and New Guinea due to the lack of diurnal ground based predators, and with the abundance of food such as figs and fruits the females could easily raise young without a father present.