For the first time a species of songbird has been found to be collectively forgetting how to sing their distinctive songs. No longer surrounded by other members of their species once they leave the nest, regent honeyeater (Anthochaera phrygia) males are failing to learn the songs of their ancestors. Instead many are copying those of more common birds, or not learning to sing at all, undermining their mating opportunities. Scientists are conducting a trial that may reverse the damage. Unfortunately, it could prove a Herculean task if, as they suspect, the same thing is occurring in other rare species.
Songbirds first evolved in Australia, and the continent was particularly rich in them, until humans started changing their habitat. The regent honeyeater is among the most affected. Dr Ross Crates of the Australian National University told IFLScience it was once found in flocks of hundreds or thousands.
Songbird males sing to woo mates, with singing quality being a prime factor in female choice. However, fathers are quiet around the nest so as not to attract predators. When regent honeyeaters were common, young males had plenty of opportunities to learn from older members of their flock come mating season. Regional dialects evolved, but commonalities could be found across their range.
Deforestation of the honeyeater's woodland habitat has caused a catastrophic decline, made worse by the 2019-20 bushfires, to the point A. phrygia is now officially classified as critically endangered. In Proceedings of the Royal Society B, Crates and co-authors report when they recorded regent honeyeaters in areas where their density is low many were not singing songs recognizable to their species.
"For example, 18 male regent honeyeaters – or around 12 percent of the total population – were only able to copy the songs of other bird species," co-author Dr Dejan Stonhanovic said in a statement. "This lack of ability to communicate with their own species is unprecedented in a wild animal. We can assume that regent honeyeaters are now so rare that some young males never find an older male teacher."
How the females know what song they should prefer is a mystery, Crates told IFLScience, but males that sing other species' songs seldom find mates, worsening the honeyeater's prospects.
Crates told IFLScience that even though such a thing has never been recorded before, the team thinks the problem may soon be widespread among other birds. (Human analogies might be more of a stretch)
Captive-raised birds are similarly songless when released into the wild, undermining major efforts to save this popular species. At best, birds raised in captivity mate with each other, causing inbreeding and losing the opportunity to learn survival skills. At worst they don't mate at all.
"So we've devised a new strategy to teach young captive regent honeyeaters to sing the same song as the wild birds by playing them audio recordings,” Crates said. Some birds with good voices have also been recruited to act as tutors for the captive young. Crates told IFLScience it is too early to measure the success of either of these programs.