Scarl, J. C., Bradbury, J. W. 2009. Rapid vocal convergence in an Australian cockatoo, the galah Eolophus roseicapillus. Animal Behavior 77: 1019-1026.

In the lecture about group recognition vocalizations we looked at several examples of animals which use vocal mimicry for group cohesion. In particular the slides about the greater spear-nosed bats and the Chimpanzee pant hoots which exhibit vocal learning and convergence are topics which are relevant to this paper. The authors of this paper were trying to determine if the galah in Australia was capable of rapid vocal convergence of contact calls to mimic a conspecific.

Many parrot species have large ranges, are non-territorial, and have fission-fusion groups, so their group members are constantly changing. This facilitates the need for them to be able to produce contact calls that are recognized by the new groups. This ability for rapid vocal modification of contact calls has been demonstrated in the Central American orange-fronted conure, so the authors wanted to know if it was also present in the galah, which is not closely related and is geographically separated, but has a similar social structure.

For this study they used a population of wild galahs living in an area northeast of Canberra, Australia, and only used the double chet contact calls for their analysis both for playback stimulus and responses. They had previously recorded double chet calls from 16 male and 10 female galahs, as part of a larger longitudinal study. All but 4 of the birds were individually marked with wing-tags. For the playback they used sites interspersed throughout the study area, which was split up into two areas, and elevated the speaker at least 1.5 m in a tree. They then recorded the responses received, and the sex of the responder.

The galahs were found to significantly modify some of the acoustic features of their contact calls in order to converge on the playback stimulus, which was most evident in the time domain measures. More males than females responded in the experiment and they both tended to converge more noticeably earlier in an interaction. They found that galahs were capable in rapid call changes during interactions lasting fewer than 3 minutes. These findings match those from the conure, leading the authors to believe that this technique maybe widespread within the parrot order.

The galahs exhibit the fission-fusion group dynamic and the group members are not permanent, so convergence may have evolved as a way to allow individuals to communicate with one another when switching groups. The imitations of group calls also serve to initiate intent to communicate and to join a group.

The authors acknowledge that they had a small sample size for females (6), and so don’t have an accurate comparison of female responses to male and female stimuli. More males responded, which suggests that the rapid convergence is used more frequently by males, but they also had a larger sample size for males (25). They also noted that the playback calls were only of one type, and so not able to change such as might be the case in the wild. This topic is interesting, but doesn’t provide much explanation for why males respond more to the stimulus.