Fig 5.

Mean ± SE. of (A) activity (i.e. the number of zone changes), (B) number of calls emitted by the subjects, (C) the time the subjects spent in zone 1 (i.e. near the loudspeaker) and (D) the time the subjects spent with crest in position 1 (i.e. erected) during the playback of white noise, partner’s and non-partners’ distress calls. Although the “time spent near the loudspeaker” and “time spent with crest in position 1” were analysed as binomial variables (see text for details), they are displayed here as a continuous variable for illustrative purposes. Regarding the time spent in zone 1, the differences between “partner” and other type of calls were not tested because no birds spent more than 15 seconds in zone 1 during the playback of partners’ distress calls (see text for details). Statistical differences between type of calls are given (***: p < 0.001; **: p < 0.01; *: p < 0.05;.: p = 0.07).