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

Understanding nest site selection is crucial for species conservation. Bird con-servation often involves installing nesting aids to increase nest site availabilityand induce colonization of unoccupied sites. However, prospecting individualsmust find nesting aids, which may be facilitated by social information. Here, we investigated the effectiveness of artificial nests and playback in the declin-ing, migratory House Martin Delichon urbicum. We selected unoccupied siteswith artificial nests along a distance gradient to occupied sites and broadcastedconspecific vocalizations during prospection times of House Martins in boththe post- and the following pre-breeding periods. Visitation and colonizationrates increased considerably in proximity to occupied sites. Playback duringthe post-breeding and pre-breeding periods enhanced visitation rates, whilepre-breeding-only and post-breeding-only playback had smaller positiveeffects. Colonization rate increased exclusively with pre-breeding-only play-back. Colonized playback and non-playback sites had similar breeding success,indicating that playback did not create ecological traps by attracting HouseMartins to suboptimal sites. Hence, broadcasting conspecific vocalizationsinforms prospecting birds of nest site availability, thereby increasing visitation,and to some degree, colonization of unoccupied House Martin sites. To boostcolonization, we recommend installing artificial House Martin nests withinapproximately 500 m of occupied sites and using playback of conspecificvocalizations.