Antipredator calls of tufted titmice and interspecific transfer of encoded threat information

Birds in family Paridae (titmice and chickadees) produce complex and distinct alarm vocalizations in response to predator encounters. In 2 controlled aviary experiments, we tested for information transfer between 2 different species of parids. We first recorded the vocal and nonvocal alarm displays of captive tufted titmouse (Baeolophus bicolor) flocks responding to presentations of live predators and controls (no animal and quail). Second, we broadcast the recorded titmouse vocalizations to captive Carolina chickadees (Poecile carolinensis) and recorded their vocal and nonvocal responses. By evaluating the situational specificity of responses by, both, titmice (production specificity, H1) and chickadees (response specificity, H2) to their respective treatments, we could test for information transfer (H3) from titmice to chickadees. Analyses revealed that information content encoded in titmouse calls completely distinguished the different predation threats presented to them (confirming H1). Similarly, chickadee responses clearly distinguished the different predator threats encoded in titmouse calls they heard (confirming H2). Responses of the 2 species were, both, parallel and threat appropriate, confirming that heterospecific information transfer occurred (from titmice to chickadees; H3). Evidence abounds that parids convey important facilitative benefits to other species within Holarctic forest bird communities. We propose that information sharing about predation threats may underlie these benefits for species that participate in communication networks with parids and suggest titmice function as community informants.