Development of the auditory brainstem of birds: comparison between barn owls and chickens

Birds have proved to be extremely useful models for the study of hearing function. In particular, chickens and barn owls have been widely used by a number of researchers to study diverse aspects of auditory function. These studies have benefited from the advantages offered by each of these two species, including differences of auditory specialization. Direct comparisons between chickens and barn owls become complicated when the degree of auditory specialization and their modes of development are brought into consideration. In this article we review the available literature on the development of the auditory brainstem of chickens and barn owls in the context of such differences. In addition, we present a time line constructed on the basis of common stages of structural differentiation, rather than chronological time. We suggest that such a time line should be considered when discussing comparative data between these two species. Such an approach should facilitate the interpretation of similarities and differences observed in the developmental processes of the auditory system of chickens and barn owls.