Say it with bowers: if male bowerbirds build it, females will come. But in the mountains of New Guinea, one species is sending mixed messages

Natural History, March, 2002 by J. Albert C. Uy

To balance the equation, we will need to compile similar records of mating activity among the spire builders. But Vogelkop bowerbirds are restricted to mountains in western New Guinea, which is now known as Irian Jaya and is administered by Indonesia. Proving more difficult to surmount than any mountain range, political instability and the recent restriction on visits to this region by scientists have prevented us from carrying out these observations. The data we have gathered so far, however, do allow us to make inferences: Spire bowers are substantially smaller than huts and are never decorated with blue or any other colorful ornaments. Because Arfak females prefer showy bowers, they might find these spire bowers unattractive or inadequate, and so might fail to see the architects as potential mates. This suggests the possible presence of reproductive barriers, but only information from the spire-building population will provide direct support for this argument. Given the political situation in Irian Jaya, testing the preferences of Fakfak females and gauging the responses of Arfak females to a Fakfak male and his spire bower may have to wait a few years.

In the meantime, the role of sexual selection in generating biodiversity is gaining attention and stimulating discussion. Current research, including my own, is now exploring why mating signals change in the first place. Do visual conditions, such as the play of light and shadow on foliage, select for certain signals that are most effective in those particular environments? Or are these changes arbitrary relative to the habitat, analogous to fads we see in our own society? In the search for answers to how species are generated, creatures as varied as fish, flies, crickets, and bowerbirds are leading the way.

J. Albert C. Uy ("Say It With Bowers," page 76) credits the writings of evolutionary biologist Ernst Mayr with sparking his interest in how new species arise. As a doctoral student at the University of Maryland, Uy began to investigate mate choice and speciation in bowerbirds, working with Gerald Borgia, a specialist in that group of avian architects. Uy, who was born in the Philippines, has done fieldwork in Central America, Ecuador, and the bowerbird lands of Australia, Papua New Guinea, and Irian Jaya, Indonesia. Now a postgraduate fellow at the University of California, Santa Barbara, he is working on speciation in paradise--kingfishers and white--bearded manakins and looking at environmental factors that could drive changes in mating signals.