The Effect of Whisper Calls on the Settlement Decisions of Female Veeries (Catharus fuscescens)
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Emerging research has shown that many species of birds utilize low-amplitude vocalizations (LAVs) in a variety of social interactions; however, the function of these vocalizations in shaping the spatial dynamics of individuals within breeding populations remains unexplored. To gain further understanding of the function of LAVs in this context, I experimentally tested the function of LAVs in the settlement decisions of a migratory songbird (the Veery; Catharus fuscescens) in a manipulated forest soundscape. I manipulated twenty plots through the playback of previously recorded male Veery songs. Half of the plots played back LAVs (i.e., whisper calls) after approximately every five songs while the other half broadcasted only the male song as the control treatment. I located thirty nests during the 4-week experiment (20 in experimental plots, 10 in control). I recorded the GPS location of each nest and monitored each nest until fledging or nest failure. Although nesting in proximity to whisper call plots was marginally non-significant, females settled at whisper call plots more often, earlier in the breeding season, and whisper call plots had a higher probability of being settled more than once. This is the first study to experimentally show how a low-amplitude signal can affect female settlement decisions.