Scientists believe they have figured out why the population of the Regent Honeyeater, a critically endangered songbird originally from Australia, is dwindling even more. The 300 remaining individuals are losing their "song culture" as there is a limited number of father figures around to teach them the proper mating songs.
The song of my people
The Regent Honeyeater (Anthochaera Phrygia) is a flagship woodland bird originally from Australia. Named after its striking yellow-and-black plumage, it mainly inhabits temperate woodlands and open forests of the inland slopes of south-east Australia. In the past decades, its numbers have been steadily declining due to the widespread clearance of forests -- but they seem to have yet another problem: they're losing their culture.
Ross Crates from the Australian University of Canberra initially set up to find the birds - which he described as finding a needle in a haystack as they occupy an area 10 times the size of the UK. When he finally saw some of them, he realized that their singing didn’t sound like a regent honeyeater – it felt like listening to another species.
"Song learning in many birds is a process similar to humans learning languages - they learn by listening to other individuals," Crates told The Guardian. "When they leave the nest, they need to associate with other older males so they can listen to them sign and repeat over time. If they don’t, they don’t know what they should be singing.”
Male regent honeyeaters spend several months in their first year learning and refining the songs they'll recite for the rest of their lives. Some learn from their fathers, but many leave the nest before they learn to sing so they need to find other mentors. But now, with only a few individuals left in the wild, this is becoming a difficult endeavor. Simply put, there are few mentors to pass the song to the next generations.
By combining historical recordings with citizen science data and five years of standardized population monitoring, the researchers looked at differences in regent honeyeater song and song complexity within and between wild and captive-bred birds. Then they examined the link between song type and population density and looked for geographical patterns.
The findings showed that the birds imitated other species such as friarbirds (Philemon), currawongs (Strepera) and cuckooshrikes (Campephagidae) – a symptom that the researchers believe is due to the loss of vocal culture. The study even suggested females are avoiding to breed and nest with males that sing unusual songs.
"When male birds sing, it's like putting out an ad saying, 'I'm over here, I'm species X, I'm Bob, and I'm really interested in finding a partner'," Scott Ramsay, a behavioral ecologist not involved in the study, told BBC. “It could be that female honeyeaters aren't even recognizing these unconventional singers as potential partners, and so they're not approaching them.”
Still, it’s not all bad news. There’s already a project to release captive-bred birds into the wild every few years to boost the population. Juveniles have first been played recordings of regent honeyeater calls from speakers inside their aviaries. Now, two adults were placed in aviaries to see if this can also help the young males to learn the right song.
The study was published in the journal Proceedings of the Royal Society B.