Data from: Experimentally provided conspecific cues boost bird territory density but not breeding performance

Decision-making during different life history stages requires information, which is obtained through own or others’ experience and interaction with the environment. In birds, song is important for territory defense and mate attraction. While song has evolved to purposely convey information it can be inadvertently exploited by conspecifics. Experiments attempting to attract focal species by playing back their song are numerous, yet the consequences for reproductive performance remain little understood. In 2013 and 2014, settlement, reproduction and extra-pair paternity of Phylloscopus sibilatrix were assessed in a randomized experiment. We hypothesized that territory number, reproductive performance and extra-pair paternity would be higher on song plots (wood warbler song playbacks during pre-breeding periods) than control plots (no wood warbler song playback). On song plots, three times more territories were established, settlement occurred faster and maximum plot occupancy was higher compared to control plots. Pairing rate, daily nest survival rate, mean clutch size, mean number of nestlings and fledglings, rates of extra-pair young, nest abandonment, and nest predation did not differ between treatments, but fledging success was lower on song plots compared to control plots. This study shows the important role social cues can play for territory selection of birds, but also exemplifies the necessity for post-attraction evaluation of reproduction to rule out negative effects of artificial attraction. Decreased fledging success on song plots and ambiguity about consequences of artificial attraction for distribution and settling dynamics of the species give reason to further evaluate whether acoustic attraction represents a suitable method for songbird conservation.