Courtship rituals take a beating as birds go off-tune

As the population of the critically endangered regent honeyeater plummeted over the years, some young birds could no longer find older ones to teach them to sing, a new study reports. As a result, the birds have failed to learn the songs they need for courtship and other evolutionary business. They try to compensate by mimicking songs from other types of birds. But because female regent honeyeaters aren’t easily moved by unfamiliar melodies, the courtship ritual is doomed to fail.

“We find that some males, if they’re not paired, just spend all their day singing, looking for a mate,” said Ross Crates, the paper’s lead author and a post-doctoral fellow at the Australian National University in Canberra. A failed tryst or two wouldn’t be a reproductive problem for a healthy population. But for a species with an estimated 200 to 400 members spread across an area of southeastern Australia that is larger than the United Kingdom, the loss of singing culture may be what the researchers called a “precursor to extinction.” The study was published on Wednesday in the academic journal Proceedings of the Royal Society B. It analyzed sightings of wild regent honeyeaters from July 2015 to December 2019, and field recordings of them from the 1980s to the present.

The researchers found that 12 percent of male regent honeyeaters in the study failed to learn any songs specific to their own species. Straying from the “regional cultural norm” was associated with reduced reproductive success, and learning to sing other birds’ tunes did not help.

“It’s an exquisite piece of work that tells a terrible story,” David Watson, a professor of ecology at Charles Sturt University in Australia who was not involved in the research, said of the new study. “It is carefully conducted science, reasonable and evidence-based inferences that, in a few short pages, describe what the extinction of a species sounds like,” Professor Watson said in an email. “It doesn’t happen with a bang but with a slow drawn-out whimper.”

The findings underscore the importance of considering animals’ cultural diversity in conservation studies, said Kristina Paxton, a post-doctoral researcher at the University of Hawaii at Hilo who has studied the songs of Hawaiian forest birds and was not involved in the Australia research. “This study adds to a growing understanding that in many animals, like humans, the loss of cultural identity can have far-ranging effects on their ability to persist,” she added.

Regent honeyeaters are a social species that once travelled in large flocks, feeding in flowering eucalyptus and mistletoe trees across an area in Australia from roughly Melbourne to Brisbane. They sing to each other not only for mating, but to mark territory and relay tips on where to find food. But as temperate woodlands across Australia were cleared in recent decades, the population fell — from about 1,500 birds in the late 1980s to about a fifth that many more than two decades later, according to government data. The species also began to lose turf battles with competitors like the noisy miner, a fellow honeyeater known for its aggressive behaviour.