Development of Bower-Building

Bower-building is a highly learned process. Young male bowers spend years learning to build increasingly complex bowers. They spend a lot of time watching the displays and bower activities of adults, and are even displayed to by the adult males. They generally do not construct their own bowers. They do, however, practice bower-building behaviors and display behaviors at the bowers of other males when the owners are away. There are also structures known as “practice bowers”, which are usually very rudimentary and may consist simply of a stick platform. Male satin bowerbirds three or four years of age appear to visit these practice bowers selectively, visiting some but not all of the ones in their home ranges, although the limited time span of the study means that this conclusion must be treated with caution. Possible factors contributing to this selectivity have yet to be identified (Maxwell et al. 2004). When they are older, they begin to build temporary bowers away from those of the adults (Collis & Borgia, 1993). The overall quality of these bowers is lower than that of bowers constructed by adults. The bowers are less sculptured, with the curvature not as pronounced (Borgia 1995). Additionally, the temporary bowers had fewer total decorations (Collis & Borgia, 1993).

Even once the bowerbirds reach adulthood, improvement can still occur. Through trial and error males can learn which specific patterns of construction are more effective in attracting females and allowing copulation. And by marauding, males can gather similar information by observing the construction patterns and mating success of other males (Kelley & Endler, 2012).

Although learning does play a large role in the development of bower-building in male bowerbirds, heredity also plays a role. Certain aspects of construction, such as decoration color choice, appear to be mediated by the individual’s cognitive and problem-solving abilities (Keagy et al. 2009),which are most likely primarily genetically determined. Additionally, males each have their own characteristic construction patterns, and these patterns are quite variable (Kelley & Endler, 2012). Such variability would be less likely if bower-building were a strictly learned process.

Additionally, there is some evidence that hormones can play a role in bower-building behavior. One study showed a positive correlation between testosterone levels and several measures of bower quality: total number of decorations, stick size, and stick density (Borgia & Wingfied, 1991).