Perception of predation risk by animals living in habitat mosaics moderates movement behaviors, potentially influencing the connectivity of landscapes. Perception of risk varies with environmental factors, which opens the possibility of managing connectivity for animals in fragmented landscapes. Observing understory forest birds wintering in north-central Florida, we tested the hypothesis that the presence of the Tufted Titmouse (Baeolophus bicolor), a vigilant, socially dominant flocking species, would increase the propensity of multispecies flocks engaged in mobbing to cross forest boundaries and move into open areas. Eastern Screech-Owl (Megascops asio) calls were broadcast next to an owl model at sites within continuous oak forest habitats (control) or just outside of forest in either old-field habitats with clustered saplings and shrub cover (shrub treatment) or in early successional habitats (open treatment; 11 trials in each habitat). In both treatments (forest adjacent to open or shrub), models were positioned 15 m from forest boundaries in nonforest habitat. For each individual responding to the playback (i.e. that entered a 30-m radius around the model), we recorded the species and its proximity to the model using three distance classes: within 15 m (at the forest edge), 10 m (out in the open), and 1 m (at the model). Both greater vegetative cover and presence of titmice were significantly correlated with proportion of responding individuals and species that approached and crossed forest boundaries, and the effects were additive. We show experimentally that socially dominant titmice can facilitate forest-boundary crossing by other bird species, which suggests a potential mechanism defining connectivity in fragmented landscapes for wintering forest birds.
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Vol. 121 • No. 3