Vocal-postural co-ordination of a sexually dimorphic display in a monomorphic species: The Barbary dove

In the Barbary dove (Streptopelia risoria L.), communication involves visual and vocal signals. In this species, behavioural interaction between sexual partners leads to changes in the reproductive hormonal condition of both sexes. At the beginning of courtship, male doves perform the bowing display. This display is composed of a stereotyped movement pattern (bowing) combined with an acoustic pattern (bow-call). In this paper, we studied the individual temporal patterning of bowing and the bow-call and how they are integrated in the display. The co-ordination between bowing movements and bow-call was analysed using a digital system for the synchronous analysis of acoustic-visual signals. Bow-calls differ between individuals in both temporal and frequency characteristics, and in their repetition rate. The bowing movements do not differ between individuals in their temporal structure but the repetition rate is individually different. The repetition rates of the vocal and postural motor patterns are highly correlated. However, the two signals are not synchronised and the phase delay between them is individually different. We suggest that in the bowing display the gender and the identity are signalled respectively by the bowing pattern and the bow-call. The integration of the two signals generates a third signal, the integrated bowing display rate. The role of the three signals during male-male encounters and during courtship behaviour is discussed