When a Bowerbird
Seeks a Mate
To
scientists, bowerbirds may be the world’s most famous birds—famous
not for their looks but for their behavior.
Each male builds an elaborate bower as a place where he can show off to females in his search for a mate. The bower may be a platform or even a little building made by weaving together twigs and grass stems. Then he decorates the bower with any pretty things he can find.
In each of the several species of bowerbirds, the males have a distinctive way of building and tending their bowers. Tending is important because the males are always trying to steal decorations from one another.
Watching
Wild Birds
To see bowerbirds in action, many scientists
have taken long trips to the wild places where the birds
live. That means the lands where northern Australia and
southern Asia almost come together.
Recently, Dr. Gerald Borgia and a team of scientists have been going there to study in detail one species, the satin bowerbird. They have used automatic video cameras and have even done some experiments to try to understand the birds’ special behaviors.
The male satin bowerbird makes a bower with two parallel walls about four inches apart and with a platform at its north end, all decorated with pretty things like colored feathers, flowers, and snail shells.
Doing Experiments
In one experiment the scientists divided 22 bowers into
two groups. In one group they removed all decorations.
Then they recorded the number of visits by females. The
results came out 15 to 3 in favor of the group with decorations.
The next year they added different kinds of decorations to see which ones the females preferred. The winners were blue feathers and snail shells. Males fight with one another for these preferred decorations. So in picking males with the prettiest bowers, females are mating with the strongest males.
Why Do They Sing and Dance?
The females also have a special set of behaviors, which
occur in three stages. First, a female inspects and compares
a whole series of bowers, usually when the males are
away.
In a second stage, the female comes back to each of several selected bowers and watches from inside as the male does a vigorous song and dance on the platform in front. Then she leaves and spends about a week building a nest. Finally, she returns to the bower of the male she has chosen as her mate.
The scientists wondered about the first stages of courtship. Which was more important to the female in making her choice? Was it the prettiness of the bower or the song and dance?
By keeping track of females, scientists found that older birds chose mainly the performance. But the younger birds seemed afraid of a male’s vigorous dance routine and made their choice based just on the decorations of the bower.
Scientists had been puzzled as to why the male bowerbird has so many different parts to his elaborate courtship. Now it is clear that the answer lies in the different ways that female bowerbirds make their choices.
