| Willow flycatcher (Empidonax traillii) populations have been in decline across California since before formal surveys were initiated in the 1970s. The California population is currently below 500 pairs. Population declines continue despite extensive conservation efforts, partially because willow flycatchers rarely recolonize sites once they have been extirpated, regardless of apparent habitat suitability. This may be because prospecting willow flycatchers assess habitat suitability by the presence of conspecifics, making them unlikely to consider unoccupied habitat as potential breeding grounds. If true, broadcasting conspecific vocalizations at unoccupied sites could help facilitate recolonization. During the 2016 and 2017 breeding seasons, we conducted an experiment to assess the effectiveness of this technique as a means of restoring willow flycatchers to suitable, unoccupied habitat. We compared recolonization rates at experimental sites where conspecific songs were broadcast during the settlement and breeding periods and at control sites where no broadcasts took place. We observed willow flycatchers at five of fourteen experimental sites during the breeding season and at one of fifteen control sites. These results suggest that broadcasting conspecific songs may be an effective way to encourage willow flycatcher recolonization where habitat has been restored. |