In bird species in which territories are defended by both sexes, 'showing up together' is a widespread behaviour of mated individuals. To test whether the spatial proximity of simultaneously appearing mates would have a territorial signal function we presented robin chats (Cossypha heuglini H.) to mounts of conspecifics placed within their territories, Experimental variables were (1) distance between mounts, and (2) number of mounts. Results: Compared to single mount presentations, residents did not show significant differences in agonistic approaches towards the 'intruders', when mounts were positioned with a distance of 3-6 m to each other (spaced presentations). In contrast, when the distance between mounts was 0.3-0.6 m, (close presentations, simulating the close perching of mates) residents approached them significantly less often and less close (Tables 1 and 2). Such approach and attack inhibitions were not stronger when three or four mounts were offered instead of two. Residental pairs spent more time in non-vocal display behaviours than did single residents (Table 3). During playback of conspecific song after having been presented to a mount test, the residents' responses appeared to be influenced by whether they had received a spaced or a close mount test before. Our results have demonstrated the significance of visual pair recognition through clues from spatial proximity of birds. As with the vocal duet displays, the close perching of pair members may function in signalling cooperation during territorial confrontation with conspecifics.