Sex-specific responses to vocal convergence and divergence of contact calls in orange-fronted conures (Aratinga canicularis)

Abstract

We investigated the signal function of vocal imitation of contact calls in orange-fronted conures (OFCs; Aratinga canicularis) in Costa Rica. OFCs live in dynamic social systems with frequent flock fusions and fissions. Exchanges of contact calls precede these flock changes. During call exchanges, the similarity between the contact calls of different individuals may either increase (converge) or decrease (diverge). We conducted a playback experiment on wild-caught captive birds in which we simulated convergent, divergent and no-change interaction series with male and female contact calls. OFCs responded differently to convergent and divergent series of contact calls, but only when we considered the sex of the test birds. Males called most in response to convergent series, whereas females demonstrated high calling rates in response to both convergent and divergent interactions. Both sexes responded most to contact calls from the opposite sex, but overall females produced more calls and had shorter latencies to calling than males. These results demonstrate that OFCs can discriminate between male and female contact calls and that subtle changes in contact call structure during interactions have signal function. The stronger overall response to convergent series suggests that convergence of contact calls is an affiliative signal.

Figure 1

Sex differences in response (mean±s.e.) of subject birds. The baseline and the test sections are represented by grey and hatched bars, respectively. Subj, subject bird. (a) Call rate, (b) latency and (c) cross-correlation similarity. Significant differences relevant to the study are indicated with asterisks.

Figure 2

Response (mean±s.e.) of male and female subject birds to male and female stimulus birds. The baseline and the test sections are represented by grey and hatched bars, respectively. Subj, subject bird. (a) Call rate, (b) latency and (c) cross-correlation similarity. Significant differences relevant to the study are indicated with asterisks.

Figure 3

Response (mean±s.e.) to convergent, divergent and no-change treatments in the test section. (a) Call rate and (b) cross-correlation similarity for the interaction between treatment and sex of the subject bird. (c) Latency for the interaction between the treatment and the sex of the stimulus bird. Stim, stimulus bird; Subj, subject bird. Significant differences relevant to the study are indicated with asterisks.