Although plasticity in signal production is well recognized as a means for animals to modify their communication systems, modifying responsiveness to signals could be equally important. We examined plasticity of responsiveness to social signals that mediate group formation and cohesion in red crossbills. The red crossbill is composed of several ecologically diverged forms, defined by variation in morphology, ecological specialization and vocal behaviour; each form is associated with a distinct variant of the species ?contact call.? To understand how plasticity in response to signal variants may influence social dynamics, we examined the response of red crossbills to distinct call variants before and after experimental pairing with [...]
