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Male bowerbirds hope to dazzle females with bright human-made items
arstechnica.
Male bowerbirds are famous for their complex mating rituals. These birds build intricate tunnels made of twigs. The structures are called bowers, and they give the birds their name. After building the framework, the males decorate the area with colorful items from their surroundings. When a female bowerbird arrives to inspect the male’s home, he tries to impress her. He tosses his shiniest objects toward her and displays his bright feathers. The goal is to attract her as a mate. The choice of decorations is a critical part of this display. The male wants to show that he is strong, healthy, and skilled.
A new study published in the journal Royal Society Open Science explores how city life changes these rituals. Researchers from the University of Exeter found that urbanization has a significant effect on Australian male bowerbirds. The main change is the availability of human-made items. Cities offer many brightly colored objects, such as plastic, glass, and wire. Rural areas, by contrast, offer mostly natural materials like leaves, seeds, and sticks. The study showed marked differences in the decorations chosen by birds in these two environments. Urban birds use far more human-made items than their rural counterparts. This difference is likely because city birds have easier access to these objects. However, the research also showed that both urban and rural birds prefer human items when given a choice.
To understand these changes, the University of Exeter researchers monitored sixty-one male great bowerbirds. They studied the birds in two locations in northern Queensland, Australia. One site was rural, called Dreghorn Cattle Station. The other site was urban, located in Townsville City. The study took place during the prime breeding season, which runs from September to December in 2023. The team photographed the decorations on each bower from above. They used both visible light and ultraviolet light. This was important because bowerbirds can see in the ultraviolet range. The researchers used an umbrella to create soft, diffuse lighting. This ensured that the colors were recorded accurately without harsh shadows.
The researchers focused on the ten decorations closest to the bower entrance. These items are the most important because the male uses them during his display. The team photographed and marked each item to identify its source. Then, they removed all decorations from the bowers. They created a large mixed pile of items from ten random urban bowers and ten random rural bowers. This pile was left at the site for three days. The male birds were never allowed to retrieve items from their own original bower. This method ensured that the birds’ choices were based on preference, not just convenience.
When the team returned, they recorded which decorations the birds had moved from the pile back to their bowers. They noted whether the items came from an urban or rural source. After the data was collected, all original decorations were returned to their rightful places. This step helped maintain the ecological balance of the study sites.