Scaling of the avian middle ear

• Published in: Hearing research 2020-09, Vol.395, p.108017-108017, Article 108017
• Main Authors: Peacock, John, Spellman, Garth M., Greene, Nathaniel T., Tollin, Daniel J.
• Format: Article
• Language: English
• Subjects: Allometry; Bird; Columella; Isometry; Middle ear; Scaling
• ISSN: 0378-5955; 1878-5891
• DOI: 10.1016/j.heares.2020.108017

This article presents a comparative study of morphology of the avian middle ear. The general morphology of the columella shows considerable variation across species, yet few studies have attempted to provide quantitative comparisons, and basic anatomical data has not been thoroughly reported. In this study, we examined the middle ear in 49 taxonomically diverse species of bird. We found significant correlations between measurements of several features (columellar length, mass, tympanic membrane area, footplate area) and interaural diameter. While scaling of columellar length with interaural diameter is consistent with isometry, masses and areas showed negative allometry, or a non-proportional scaling with interaural diameter. These observations remained true even for species with unusual middle ear morphology, such as Alcedinidae (Kingfishers) in which the basal struts of the columella form a structure almost resembling a mammalian stapes, or Tytonidae (Barn Owls) which have a highly bulbous footplate. It therefore appears that allometry cannot help explain the morphological variation in the columella. •Columellar length appears to scale isometrically with interaural diameter.•The footplate area, tympanic membrane area, and extracolumellar length show negative allometric scaling.•Columellar morphology shows striking variation across taxa, but the scaling relationships appear consistent.