From the male gentoo penguins who present their precious pebbles to their intended partner to the Darwin bark spiders who give oral sex to stop themselves from being eaten, courtship behavior can range from the wonderful to the downright weird in the animal kingdom. These rituals can be crucial for successful sexual reproduction and for the male Java sparrow, simply serenading females is not enough. These birds coordinate their songs with clicking sounds similar to a drum, according to the latest study published in the open-access journal PLOS ONE.
Researchers from Hokkaido University studied how birds were able coordinate the clicking sounds from their beak—known as their ‘bill’—with the songs they produced when they sing. The study analyzed archived recordings from 30 domesticated adult males. Of these birds, 22 were related, including nine fathers and their sons. The other males were experimentally reared and not exposed to clicking sounds.
While previous studies have reported that some species with vocal learning capacity can also spontaneously synchronize their movements with musical rhythms, only a few have tried to address the question of how animals can temporally coordinate multiple communication signals. In this latest investigation, researchers studied the frequency of the bill clicking, how it was coordinated with song notes and whether this coordination was a learned behavior.
“We found that bill-click sounds were observed at a high rate before and after specific notes in songs. It’s just like humans clapping their hands when singing,” lead researcher Masayo Soma tells IFLScience.
Older birds produced clicks during almost every song, but this was not the case for younger adults, which suggests that these clicks are added on after they have learned the song. While these percussionist-like beats were coordinated with song notes, researchers need to further investigate whether this is a learned behavior.
“What we can say is that bill-clicking behavior itself is intrinsic because we observed that Java sparrows that had been reared in social isolation also produced bill clicks. However, song-click association is similar between social fathers and sons. So, it is possible that the coordination between singing and clicking is learnt,” says Soma.
Non-vocal sound production is quite a rare phenomenon in birds that are vocal learners, Soma says, as the majority of the cases of non-vocal sound production are reported in non-vocal learner species, such as pigeons and woodpeckers. She suggests this may be due to the limited variety of vocal patterns that non-vocal learners have.
“In this sense, it would be really important to look into why Java sparrows evolved to have non-vocal sounds in addition to learning-based vocalizations in future studies," she tells IFLScience. "Their behavior may be key to understanding the coordination of movement with sound."