Producer
RONNIE GODEANU

Writer
DAVID MALAKOFF

Art Director
SABINA DALEY

Graphic Artist
MICHAEL PITTARD

Production Artist
MEIZA FLEITAS

Technical Director
BRIAN PATRICK LEE

Scientific Consultant
GIANNA SCARALIA

Thirteen Online is a production of Thirteen/WNET New York’s Kravis Multimedia Education Center in New York City. Anthony Chapman, Director of Interactive & Broadband.

© 1997 Thirteen/WNET New York

All Rights Reserved

Television Credits

A Co-Production of Thirteen/WNET New York and BBC-TV in Association with Partridge Films

Funder Credits

Funding for the TV series NATURE is made possible in part by Park Foundation. Major corporate support is provided by Canon U.S.A., Inc., Ford Motor Company, and TIAA-CREF. Additional support is provided by the nation’s public television stations.

We recommend these Web sites for those interested in the subjects shown on the program. All links are valid as of September 1, 2000.

Everything About Bowerbirds
http://birding.about.com/hobbies/birding/msub1-bowerbirds.htm
About.com’s useful links to information about many types of bower birds.

Australian Rainforest Birds
http://www.birdwatching-australia.com
See the Brush turkey, bower birds, and 13 other species at this site, sponsored by an Australian lodge catering to birdwatchers.

Why Do Bower Birds Build Bowers?
http://www.sigmaxi.org/amsci/articles/95articles/gborgia.html
Illustrated summary of an article by bower bird expert Gerald Borgia from the November-December 1995 issue of AMERICAN SCIENTIST.

Great Minds Build Bird Brains
http://www.isr.umd.edu/ISR/publications/newsletter/sswi97/robobirds.html
How and why University of Maryland scientists built robotic Satin bower birds.

Australia’s Rainforests
http://www.gullivermedia.com.au/rainf.html
Snapshots of these magnificent forests from an Australian film company. Includes bower bird and Brush turkey pictures.

Print Resources

A Brush turkey tends to incubating eggs.

For those interested in the subjects shown in BOWER BIRD BLUES, we recommend the following books and print articles.

Bergamini, David. THE LAND AND WILDLIFE OF AUSTRALIA. New York: Time Inc., 1964.

Blakers, M., and S.J.J.F. Davies. THE ATLAS OF AUSTRALIAN BIRDS. Melbourne: Melbourne University Press, 1985.

Bransbury, J. WHERE TO FIND BIRDS IN AUSTRALIA. Melbourne: Waymark, 1992.

Breeden, Stanley, and W.T. Cooper. VISIONS OF A RAINFOREST: A YEAR IN AUSTRALIA’S TROPICAL RAINFOREST. Boston: Ten Speed Press, 1996.

Pizzey, G. A FIELD GUIDE TO THE BIRDS OF AUSTRALIA. Sydney: Collins, 1980.

Vandenbeld, John. NATURE OF AUSTRALIA: A PORTRAIT OF THE ISLAND CONTINENT. New York: Facts On File, 1988.

A female bower bird considers her options.

Gerald Borgia, a University of Maryland bower bird expert, believes the different kinds of bowers all serve essentially the same function: to make visiting female bower birds feel comfortable by protecting them from overeager males. Courtship rituals, he notes, almost always involve males and females standing with the bower between them, like a fence. In the case of the maypole-building Macgregor’s bower bird, for instance, the courting pair warily circles the central tower. Only when the female chooses to stop and allow the male to approach can mating occur. “The bower probably started as a protective device,” Borgia concludes. “It allows females to get close enough to get a good look without feeling threatened. The male that builds something that makes the females feel most comfortable is likely to see more females.” Borgia has also detected a relationship between bower type and intensity of the male’s display. The male Spotted bower bird, for instance, builds a wide straw wall and performs a relatively energetic display full of dance steps and dramatic poses. In contrast, species building smaller barriers have toned-down displays that are probably less threatening to females.

A male bower bird checks his handiwork. Other researchers have noticed a link between the showiness of a bower bird’s plumage and the intricacy of its bower: in general, the drabber the bird, the fancier the bower will be. Some believe this reflects an evolutionary choice: drab birds compensate for their dull appearances by building flashier nests.

A male bower bird checks his handiwork.

Borgia has also noticed that bower complexity sometimes varies with topography. For instance, species living on hilltops build more modest bowers than those living in valleys. The explanation, he says, may be the amount of light that penetrates the forest in the two kinds of habitat. Ridge tops are often shrouded in clouds, allowing only dim light. Hence, to best show off their decorations, bower birds living here may build more open bowers to make best use of available light. In contrast, light is less of an issue in the valleys, so bower birds can afford to have more elaborate roofed structures.

Surprisingly, Borgia has found that bower birds that build similar-shaped bowers aren’t necessarily closely related to each other. Using a DNA fingerprinting technique, he and his colleagues drew a family tree for bower birds that showed their evolutionary relationships. It suggested that species that evolved at different times have independently learned to build similar kinds of bowers, possibly because they faced similar kinds of environmental conditions.

But close observation can reveal important differences in the seemingly-similar structures, Borgia says. Where one species may build its bower from the bottom up, for instance, the other may start a similar structure at the top and build down. Similarly, some species put the entrance to their bowers on the uphill side, while similar structures built by other species face downhill. Nobody knows whether young bower birds learn such practices from their elders, or whether they are encoded in their genes at birth. It is a much-debated question that Borgia hopes to answer in future studies by rearing native males in captivity with and without mature tutors.

Videocameras notice when a bird approaches.

One practical problem that any would-be researcher faces, explains Gerald Borgia, an expert on bower birds at the University of Maryland, is that “it’s hard to find bowers.” Since 1980, however, Borgia and his students have been developing clever techniques for finding and observing courting birds in a square mile of rainforest near Wallaby Creek in northeastern Australia. To find Satin bower bird bowers, for instance, Borgia stages intense searches. “We get a bunch of volunteers, form lines maybe six abreast, and walk the site,” he explains. But finding a bower doesn’t ensure a study’s success, because an observer might watch it for hours before seeing any courting activity. So automatic cameras are left to keep watch on the bowers instead. Early on, Borgia used 8-millimeter film cameras; today, videocameras equipped with hair-trigger laser sensors start recording the action whenever a bird approaches the bower.

In a recent study, cameras trained on 36 bowers allowed Albert Uy, one of Borgia’s graduate students, to study the practice of “mate shopping.” The question, Borgia explains, was “How many bowers did a female visit before choosing a mate?” Surprisingly, preliminary results suggest that only 25 percent of the monitored females shopped around; the rest went right to a single bower. As the scientists analyze the more than 2,300 hours of videotape they have accumulated, more answers are likely to emerge. The mate-shopping pattern seen so far could reflect the fact that bower birds are relatively long-lived (Borgia has tracked one female for 17 years), meaning they remember the “best” males from previous years. Longevity may also explain another pattern: males tend to build bowers in about the same places year after year.

Bower birds can be hard to study.

Bower birds can be hard to study. If nothing else, Borgia says, the predictability makes it easier for the researchers to relocate the bowers.

Another of Borgia’s graduate students, Gail Patricelli, is using robotic bower birds to study how courting bower birds communicate. “The problem,” Borgia explains, “is that you don’t know which part of the male’s display is being stimulated by the female’s behavior, and which is intrinsic to males. Gail wants to find out what kind of cues the females are sending out.”

To do that, engineers at the University of Maryland built three robot bower birds for Patricelli that are able to perform simple movements such as ruffling their feathers, opening their wings, turning their necks and crouching. In October, Patricelli began placing the robots in bowers, operating them by remote control, then videotaping how the males respond. Borgia reports that the robots are so lifelike that males attempted to mate with them. Final conclusions, however, will have to wait for the scientists to finish analyzing the tapes, which could take years. In the meantime, bower birds and Australia’s other unique animals will continue to fascinate scientists — and confound casual observers unused to the island continent’s unique twist on life.

A Satin bower bird.

Today, one of the best places to see some of these unique plants and animals is the rainforest of eastern Australia. These misty woods are the dramatic setting for the NATURE program, Bower Bird Blues. At first glance, some of the creatures you’ll see may look familiar. The waddling, sharp-snouted echidna, for instance, looks much like a porcupine or a hedgehog. But it is no ordinary mammal: it is a monotreme, a kind of living fossil that lays lizard-like eggs and incubates them in a pouch. Similarly, the plump Brush turkey looks much like the Toms destined for our Thanksgiving tables. But this is a turkey with a twist: the male builds an enormous mound of rotting leaves, inside of which it incubates eggs. The eggs, however, don’t hold his young — his are being babysat by another male mound-builder! The mutual-aid arrangement helps females ensure that their eggs get careful care.

The star of this unusual menagerie, however, is the male bower bird, an accomplished avian architect that has long fascinated scientists with its remarkably complex courting behavior. Instead of using just showy plumes or a romantic melody to attract a mate, the pigeon-sized bower bird constructs an elaborate structure — a bower — on the forest floor from twigs, leaves, and moss. It then decorates the bower with colorful baubles, from feathers and pebbles to berries and shells.

The bowers aren’t nests for raising kids; they are bachelor pads designed to attract and seduce one or more mates. When a female arrives to inspect the bower, the male struts and sings. He hopes to convince her to enter the bower, where mating takes place. The female then flies off to build a nest close by, leaving the male to try to convince another female to join in a romantic tryst. Bower birds “exhibit pretty extreme display behaviors,” says Gerald Borgia, a University of Maryland, College Park, biologist who has been studying the birds for nearly two decades. As a result, he says, they are of special interest to scientists seeking to understand how such complex traits evolve and function. His research team, for instance, is using trip-wired surveillance video cameras and robotic birds to probe the hidden world of the bower bird.

A bower bird builds his “bachelor pad.”

A bower bird builds his “bachelor pad.” Overall, there are 17 kinds of bower birds in Australia and on the neighboring island of New Guinea. Some are known as catbirds, while others are called “gardeners” or “stagemakers.”

Each builds its own shape of bower and prefers a different decorating scheme. A few, for instance, surround their bowers with carefully planted lawns of moss. Others have been known to steal shiny coins, spoons, bits of aluminum foil — even a glass eye — in an effort to create the perfect romantic mood. Some, like the iridescent blue Satin bower bird, the star of Bower Bird Blues, even “paint” the walls of their structures with chewed berries or charcoal. For the male Satin, which builds a U-shaped bower from parallel walls of twigs, the favored color is blue. To decorate its “avenue,” as scientists call it, he collects blue feathers, berries, shells, and flowers. While some of these decorations are found in the forest, others are stolen from the bowers of other males; young males, in particular, are prone to this petty thievery. However obtained, the precious knickknacks are then scattered around the bower. The male then waits, passing time by constantly fine-tuning his structure and rearranging the decorations.

For many males, the effort will be mostly futile. A younger male, for instance, may be able to seduce only a single one of his dozens of visitors — or none at all. Indeed, many males get not even a single glance: in a recent study, 75 percent of female birds visited only one bower before mating. In contrast, older males often have potential mates constantly stopping by for a peek. These more experienced suitors may mate with dozens of different females in a single breeding season.

To order a copy of Bower Bird Blues, please visit the NATURE Shop.
Online content for Bower Bird Blues was originally posted April 1997.