Apr 14th, 2009
May The Best Architect Win
We have heard of males impressing females with colourful plumage, melodious singing, physical strength, ability to source for food and the like. However, the Australian male Bowerbirds are more interested in building bowers and displaying in them all the bright and colourful items that they have collected. The male bower birds do not simply collect items from nature like flowers, berries and leaves. They even collect man-made products like bits of aluminium foil; basically anything shiny or colourful. For 9 to 10 months, they painstakingly arrange and rearrange their collections so as to achieve the most impressive arrangements. Their attempts at creating a beautiful interior to impress females do not stop at that. The highly creative male bowerbirds also “paint” the interiors of their bowers with chewed berries, plant juice or charcoal so as to increase the attractiveness of their bowers.
However, female bower birds are easily impressed. That, or male bower birds all build equally outstanding bowers. In a recent study, 75 per cent of female bower birds mated with the owner of the first bower they visit. Female bower birds also tend to return to the males that they have mated with before. Therefore, a younger male bower bird is usually at a disadvantage, sometimes only getting to mate with one in a dozen female visitors to his bower.
Interesting, male bower birds do not depend solely on impressive bowers during courtship. Their sexual displays also consist of “song mimicry, ritualized prancing, and brilliant plumage coloration”. All of these sexual displays can reveal a lot of information about the males; from their body sizes to their health conditions. For example, a bright plumage may hint at a male’s parasite load while bower quality can predict body size (Stéphanie M. Doucet and Robert Montgomerie, 2002). This is because a physically larger bower bird may have an advantage when it comes to stealing ornaments from other bower birds. Therefore, these sexual displays often shape a female bower bird’s choice of a mate.
Image courtesy of bdonald.
References
“Bower Bird Blues” Nature. April 1997.
Stéphanie M. Doucet and Robert Montgomerie, 2003. Multiple sexual ornaments in satin bowerbirds: ultraviolet plumage and bowers signal different aspects of male quality. Behavioral Ecology, 14(4): 503-509
I wonder if there is a certain preference for colour/ layout that attracts the female bower birds? Maybe that’s why the ‘more experienced’ (aka older) birds can attract more females to visit them?