Figure 2.

Mean number of birds perched in the trees near the loudspeakers + SE in the baseline phase (grey bars) and the treatment phase (black bars) for the dyads with varying familiarity pairings (F = familiar to the local group; U = unfamiliar to the local group). Values represent the difference in response between the speaker that played the calls of a male and the speaker that played the calls of a female (Δ♀-♂) and we added 4 to eliminate negative values. **P < 0.01; *P < 0.05.