Voice breaking in adolescent red-crowned cranes (Grus japonensis)

Voice breaking is a process associated with puberty of human males that also occurs in adolescence in some birds. This study reports the jump-like vocal changes occurring during voice breaking in adolescent red-crowned cranes (Grus japonensis). We investigated acoustic parameters of chirp and trill calls during vocal ontogenesis from hatching to the age of 1.5 years in 17 male and 31 female captive red-crowned cranes and compared them with definitive calls of 5 male and 8 female conspecific adults. During voice breaking, trills and chirps of both sexes contained two non-overlapping independent fundamental frequencies: the upper one, representing the retained juvenile frequency, and the lower one, the newly attained adult frequency. Before voice breaking, the calls contained only the upper frequency, whereas after it only the lower one. Voice breaking occurred between the age of 7 and 11.5 months. We test whether sex, dates of birth and body mass gain are associated with voice breaking and speculate whether voice breaking triggers the disruption of the parent chick bond or vice versa, or both events are driven by a third, yet unidentified trigger.