Playback experiments highlight the importance of nearest‐neighbor distance and social information for nest site selection in the House Martin ( <i>Delichon urbicum</i> )

Abstract Understanding nest site selection is crucial for species conservation. Bird conservation often involves installing nesting aids to increase nest site availability and induce colonization of unoccupied sites. However, prospecting individuals must find nesting aids, which may be facilitated by social information. Here, we investigated the effectiveness of artificial nests and playback in the declining, migratory House Martin Delichon urbicum . We selected unoccupied sites with artificial nests along a distance gradient to occupied sites and broadcasted conspecific vocalizations during prospection times of House Martins in both the post‐ and the following pre‐breeding periods. Visitation and colonization rates increased considerably in proximity to occupied sites. Playback during the post‐breeding and pre‐breeding periods enhanced visitation rates, while pre‐breeding‐only and post‐breeding‐only playback had smaller positive effects. Colonization rate increased exclusively with pre‐breeding‐only playback. Colonized playback and non‐playback sites had similar breeding success, indicating that playback did not create ecological traps by attracting House Martins to suboptimal sites. Hence, broadcasting conspecific vocalizations informs prospecting birds of nest site availability, thereby increasing visitation, and to some degree, colonization of unoccupied House Martin sites. To boost colonization, we recommend installing artificial House Martin nests within approximately 500 m of occupied sites and using playback of conspecific vocalizations.