Syntax errors do not disrupt acoustic communication in the common cuckoo

Abstract

When acoustic communication signals are distorted, receivers may misunderstand the signal, rendering it ineffective. Common cuckoos (Cuculus canorus) are popularly known for the males’ simple, two-note advertisement calls, the “cu-coo” used for declaring the male’s breeding territories. Cuckoos do not learn their calls (vocal non-learners), so they are expected to have a limited ability to produce different acoustic signals. Nevertheless, male cuckoos appear to make syntax errors (e.g., repeated, reversed, or fragmented elements) even in their simple advertisement calls. We conducted a playback experiment with male cuckoos, broadcasting ten call types, including seven modified calls with errors (e.g. “cu-cu”, and “coo-cu”) and three natural calls used for comparisons (“cu-coo”, “cu-cu-coo”, and interspecific control). Male cuckoos responded in a manner suggesting that the presence of the first (“cu”) note of the natural 2-note “cu-coo” call in any form or combination yield effective signals. However, through the elevated frequency (by about 200 Hz) and greater speed of the “cu” note, the natural 3-note version “cu-cu-coo” call appears to have gained a novel communicative function in signalling with female cuckoos. Thus, syntax errors in calls with the “cu” element are not responsible for changing the function of the male cuckoos’ “cu-coo” call.

Editorial: Evolution and Function of Acoustic and Visual Signals in Avian Brood Parasitism

“…However, Wang Y. et al found no evidence that these calls affected host response and was insufficient for suppressing bird activities. Unlike female cuckoo vocalizations, male cuckoo calls do not have any apparent role in countering host defenses and instead are sexually selected (Moskát et al, 2017;Moskát and Hauber, 2022). Esposito et al analyzed acoustic variables and visual display sequences of male common cuckoos to determine whether these signals are multimodal by nature and complement one another as is known to occur in other brood parasites (O'Loghlen and Rothstein, 2010).…”