Listen closely to a Java sparrow sing: Interspersed among the notes will be clicks that the bird makes with its bill. All male birds use the clicking sounds in their songs — and the patterns appear to be passed from father to son, a new study reports.
Masayo Soma and Chihiro Mori of the Hokkaido University in Japan analyzed recordings of 30 male birds. These were a domesticated version of the species Lonchura oryzivora, which is native to the Indonesian islands of Java and Bali (and on the decline because so many have been trapped for the pet trade). Twenty-two of the birds were related (fathers and sons or foster sons), seven were reared in isolation and the last bird grew up among Bengalese finches that don’t make clicking sounds. The results of the analysis were published May 20 in PLOS ONE.
The click sound can be produced without learning, Soma and Mori found. All the birds, including those that were reared on their own and never heard another Java sparrow, sang songs that included bill clicks at least some of the time. Older birds produced the sounds in almost every song; younger ones less often. They appeared to get the hang of the sound and incorporating it into songs by about six months of age, the researchers found.
But there was some transfer of knowledge from father to son. Within these pairs of birds, there were similarities in their songs. Fathers and sons tended to use clicking sounds at the same rate in their tunes. Sons learned 68 to 90 percent of dad’s repertoire, and those that were the best learners incorporated more clicks into what they sang.
Soma and Mori then looked at the 18 birds that clicked most often, in more than 60 percent of their songs. They found that the birds tended to click more frequently at the beginning of songs and before and after specific notes. The clicks appear to be integral parts of certain syllables within the songs, the researchers say.
“The question of why Java sparrows use nonvocal sound communication in addition to singing remains a puzzle,” the team writes. Female birds also make the sounds, but their vocalizations have yet to be analyzed. The clicks may be involved in courting, but it’s unclear for now how such a complex communication system evolved.