The hearing capabilities of the Dromornithidae (Aves), with inferences on acoustic communication and ecology

The hearing abilities of birds, specifically the mean hearing frequency and best hearing frequency range, have been correlated with the length of the endosseous cochlea duct (ECD), a sensory organ of the inner ear. The giant, flightless Australian dromornithid birds (Aves, Dromornithidae) are wholly extinct so inferring biological attributes from extant relatives is impossible. A key attribute to understanding how these birds behaved and interacted with the environment is hearing ability. The preservation of osseous structures which enclose the ECD within the skull provide a basis for interpreting dromornithid hearing capabilities. Measurements of the ECD were analysed against a measurement of skull size using regression analyses to test whether the length of the dromornithid ECD follows the allometric scaling trajectory reported for this sensory organ in other birds. Hearing capabilities were then calculated using previously reported algorithms for best hearing frequency range and mean hearing frequency. Although especially short in dromornithids, the length of the ECD relative to basicranial length generally conforms with the negative allometric relationship with body mass observed in other birds. However, compared to other birds, the estimated dromornithid mean hearing frequency was especially low, and their hearing range was narrow. These results support reconstructing dromornithids as low-frequency sound producers enabling acoustic communication over long distances and in closed vegetated environments with implications for foraging and breeding ecology.