Vocal Contextual Learning in Birds

Vocal production learning, in which the structure of vocalizations is learned, has a narrow distribution among animals in general and among birds in particular. Here we assess the generality of two other forms of vocal learning: comprehension learning, in which response to vocalizations is modified by experience with how the signals are used by others, and usage learning, in which the contexts in which vocalizations are produced is similarly modified. Evidence for vocal comprehension learning is shown to be widespread, occurring in 17 of 37 avian orders representing all of the major lineages except for the most basal one. Evidence for vocal usage learning, by contrast, is extremely limited, occurring in only four of the avian orders in two of the major lineages. Furthermore, some instances of vocal comprehension learning are more cognitively advanced than what is found in vocal usage learning. Although the distribution of evidence for comprehension and usage learning may in part result from the distribution of research effort, these results suggest that the ability to extract information from sounds is better developed in birds than is their ability to encode information in sound. These patterns have implications for the evolution of language.