Bower construction in the Vogelkop bowerbird

All bowerbirds are classified into the family Ptilonorhynchidae, which is split into 5 genera with 20 individual species. All genera of Ptilonorhynchidae are found in Australia, with 4 also being found in New Guinea. Bower birds are famous for their intricate and elaborate bower-building, where the males will construct bowers that were known to baffle early scientists, leaving them to wonder how such a relatively small bird can create such structures. Some bowers have been recorded to be up to approximately two meters in diameter and one a half meters high. They are often decorated with display objects, which show off the males foraging abilities, and are meticulously maintained in order to attract females (Rowland 2008).

"Bowerbird putting its nest back in order" <http://www.flickr.com/photos/reevco/11061941235/in/set-72157638069778654>

The bowerbirds of Australia and New Guinea have been extensively studied since their discovery, with the cryptic characteristics of many species being slowly unravelled. One species that has been the focus of attention relatively recently is the Vogelkop Bowerbird.

Through their study of allopatric populations (populations that are geographically separated and have no mixing of genes) of the Vogelkop Bowerbird, Albert, Borgia and Uy (2000) tested the hypothesis of speciation through sexual selection, as well as the hypothesis that changes in male displays are driven by female choice.
It was known that in some of the populations studied there were similarities between the type of bower and display that was constructed, and that these constructions were completely different to those of other populations in the study. Two types of bower construction were observed in this study, as seen in the photo below, one being a large hut like structure (A) that is elaborately decorated with bright objects, and the other being a 'maypole' construction (B), decorated in dull objects.

Bower constructions in allopatric populations of the Vogelkop Bowerbird 

In a newly diverged populations, Albert et al expected to see significant differences in female preferences and corresponding male display traits in the absence of substantial genetic and morphological differences. During their study they experimentally demonstrated distinct decoration colour preference in males, provided evidence of female preferences for differing decoration and bower traits and provided evidence that there is little genetic variation between the Vogelkop Bowerbird populations. By doing this, they were not only able to observe these expected differences, prove their original hypotheses to be true, but also use the Vogelkop Bowerbird to show that display trait divergence within populations, which is known to cause rapid speciation, is driven by sexual selection.



References:
- Rowland, P 2008, Bowerbirds, CSIRO Publishing, Australia 
- Albert J, Uy C, Borgia G, 2000, 'Sexual Selection Drives Rapid Divergence in Bowerbird Display Traits', Evolution, vol. 54, no. 1, pp. 273-278
- Barry Reeves, 2013, Bowerbird putting its nest back in order, Flickr, viewed 1st April 2014 <http://www.flickr.com/photos/reevco/11061941235/in/set-72157638069778654>