Joint-nesting smooth-billed anis, Crotophaga ani, use a functionally referential alarm call system

Accurate, threat-specific alarm systems might play a role in the evolution of joint-nesting systems by offsetting the high costs associated with joint nesting. The smooth-billed ani, a joint-nesting cooperatively breeding bird, produces at least two distinct classes of vocal alarms. Anis give ‘chlurp’ calls in response to flying raptorial birds, and they give ‘ahnee alarms’ in response to terrestrial threats. We used acoustic playback to test …