Study finds urban male bowerbirds in Queensland use human-made objects in courtship displays far more often than rural birds

Male bowerbirds have long been known as some of nature's most creative romantics. To attract a mate, they spend weeks or even months building elaborate structures known as bowers and decorating them with carefully selected objects.

Now, researchers have found that many birds are increasingly turning to human-made debris to enhance their displays.

In a new study published in Royal Society Open Science, available through ResearchGate, researchers found that urban male great bowerbirds in Queensland, Australia, are using items like glass, plastic, and wire to adorn their bowers. They say that these birds are far more likely to decorate their bowers with human-made objects than their rural counterparts, and this trend could be changing one of the animal kingdom’s most remarkable courtship displays.


City birds are using more human-made objects

According to Royal Society Open Science, available through ResearchGate, the study led by behavioural ecologists Caitlin Evans and Laura Kelley of the University of Exeter examined 61 great bowerbird bowers in northern Queensland during the birds' 2023 breeding season.

They observed that urban bowers contained substantially more human-made decorations than rural bowers. The findings involved researchers comparing displays in the centre of Townsville City with those located on the rural Dreghorn Cattle Station.

The research also found a stark difference between the two populations. Birds in rural areas tended to use naturally occurring items such as seeds and leaves in their bowers, whereas birds in the city opted for items like coloured glass, fragments of plastic, and wire.

According to the University of Exeter's research summary, urban bowers contained far more decorative items on average than rural bowers. One particularly enthusiastic male had collected more than 300 objects around his display area.

Some of the items were surprisingly unusual

The list of decorated items included several surprising examples, with some, such as medicine bottles near a hospital, fluorescent mouthguards next to a sports field, and even a pair of handcuffs discovered around city bowers.

“Our findings show that bowerbirds in a city use a wide range of items scavenged from humans,” stated the lead researcher, Caitlin Evans.

These birds are known to gather objects from all over their territory and are infamous for pilfering choice trinkets from rivals. It’s not unheard of for local residents to keep their garage doors shut as bowerbirds have been known to slip inside in pursuit of nails, screws and other shiny baubles.

Human-made objects appear to be preferred by males

To determine whether urban birds passively collected items due to their availability or actively preferred human objects, researchers set up an experiment. They created piles of both urban and rural decorations and offered them to male birds, returning three days later to see which objects they had collected.

The study found that male birds from both regions significantly preferred human-made decorations over natural ones, selecting human-made items far more frequently than natural decorations.

Even birds in rural areas showed a preference for urban objects over natural decorations, found Dr Evans, indicating that the attraction isn’t exclusive to the city birds.

Why are bowerbirds attracted to junk?

One possible explanation, suggested by behavioural ecologist Daniel Baldassarre, is that novelty may play a role. As the birds often use brightly coloured elements to attract mates, they are naturally attracted to novel colours and materials.

Thus, glass, plastic, and wire may be appealing for their ability to offer rare or strikingly unusual colours, or for their attractive reflective qualities. Furthermore, human-made materials such as plastics and metals don’t decay quickly, unlike natural fruits, leaves or flower petals, giving males a more enduring display.

A reminder of how humans influence wildlife

While scientists remain uncertain of the long-term impacts, such as whether females favour males with these "trash displays" and if this alters reproduction, they acknowledge potential risks. Past studies on related satin bowerbirds have demonstrated that birds sometimes ingest and are injured by human trash such as plastics.

Nonetheless, the finding that bowerbirds are incorporating human debris into their ancient courtship rituals highlights an unexpected way in which wildlife is adapting to landscapes reshaped by human activity.

“We don’t yet know if this has any negative or positive impact on them, but it’s a reminder of how human activity is changing the natural world in unanticipated ways,” said co-author Laura Kelley, according to Smithsonian Magazine.

For now, the birds appear to be incorporating human-made objects into their courtship displays.