SONGS AND CALLS: PERSPECTIVES ON CREATING A GLOBAL DEFINITION

Bird vocalizations have been split historically into two main categories: calls and songs. This categorization has been based mainly on the duration and complexity of the vocalization, although other criteria including function, development, and phylogeny have been included to separate both vocalizations. The increasing number of studies over the last decade examining the structure, function, and evolution of vocalizations, especially for species that breed in the tropics, have revealed that the current definitions for songs and calls no longer match our current knowledge of bird vocalizations. Here, we propose a new global definition for calls and songs that matches our current knowledge on this topic. Additionally, we review several key assumptions that have been used to classify songs, and by association calls, and we present clear examples that contradict these previous assumptions, and thereby limit the definition of songs and calls. Our proposed call and song definitions correct for the ambiguity of previous definitions that use complexity and duration, or omit vocalization functions, and reflects the diverse and multifunctional properties of avian vocalizations.