Post-breeding courtship: public information about breeding habitat quality?

Animals can estimate breeding habitat quality by monitoring social information provided by the behaviours of others. While it is accepted that the value of public information erodes with distance from the source of information, the spatial and temporal ecology of public information acquisition and use is not well understood. Published accounts of the acquisition of public information for breeding habitat selection show a study bias towards the period corresponding to the breeding season. Here, we explored the idea that post-breeding courtship is a reliable source of performance social information about breeding habitat quality that can be used by nest-site prospectors. We revealed that post-breeding courtship can be used as performance social information for breeding habitat selection in a sedentary, cavity-nesting bird species, the Eurasian Tree Sparrow Passer montanus. First, the occurrence of the autumn nest at a nest box was positively associated with the nest box’s breeding performance in both the preceding and subsequent breeding seasons. Second, nest boxes with owners that showed higher post-breeding courtship activities attracted more prospectors. Namely, more prospectors visited nest boxes momentarily occupied by both owners and containing complete autumn nests at the end of autumn compared to nest boxes momentarily occupied by single owners and containing incomplete autumn nests. We suggest that post-breeding courtship represents performance social information about breeding habitat quality that is accessible to more potential observers than performance social information available during the breeding period is. Also, post-breeding courtship can be even more reliable performance social information than that available during the breeding period because it integrates information provided by informed individuals on the nest site’s breeding performance and post-breeding attractiveness (i.e. use).