Avian middle ear adaptations in aquatic in diving birds + Euryapteryx (moas genus) species diversity
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Ben Creisler
Apr 20, 2026, 7:39:34 PM (6 days ago) Apr 20
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Ben Creisler
Recent avian papers:
John Peacock (2026)
Adaptation in the Avian Middle Ear—The Columellar Annular Ligament in Aquatic and Diving Birds
Journal of Morphology 287(4): e70124
doi: https://doi.org/10.1002/jmor.70124
https://onlinelibrary.wiley.com/doi/10.1002/jmor.70124
Free pdf:
https://onlinelibrary.wiley.com/doi/epdf/10.1002/jmor.70124
The effective detection of environmental vibrations such as sound waves depends on the transmission of tympanic membrane motion through the middle ear to the inner ear hair cells. In birds, the bony element of the middle ear is the columella; its distal end joins the cartilaginous extracolumella and tympanic membrane, while its basal expansion (the footplate) interfaces with inner ear fluid at the oval window, where it is held in place by the stapedial (columellar) annular ligament. Variation in footplate and oval window geometry can alter the annular ligament's size and shape, thereby influencing middle ear mechanics. Previous studies have noted relatively small footplates in aquatic birds as compared to their terrestrial relatives, and suggested that the adaptive significance of these may relate to their influence on the relative size of the annular ligament. Here, I examine a taxonomically and ecologically broad sample of bird species to test the hypothesis that aquatic lineages have convergently evolved proportionally larger annular ligaments. Results show larger ligaments are characteristic of aquatic, and particularly diving species, while narrower ligaments occur in high-frequency specialists. These patterns are polyphyletic and, alongside their strong ecological associations, indicate repeated functional adaptation of the middle ear. Larger ligaments are consistent with reduced system stiffness and enhanced low-frequency transmission, a hypothesis which is plausible for pelagic seabirds. In contrast, the extreme ligament enlargement in diving taxa is unlikely to be related to hearing, and instead may play a role in protection from barotrauma.
Richard N Holdaway, Morten E Allentoft, Matt J Rayner, Andrea A Cabrera, Alba Rey-Iglesia, Eline D Lorenzen & Michael V Westbury (2026)
Multiproxy analysis of the extinct moa genus Euryapteryx reveals new phylogenetic structure and disparity with morphometrics
Biological Journal of the Linnean Society 147(4): blag018
doi: https://doi.org/10.1093/biolinnean/blag018
https://academic.oup.com/biolinnean/article-abstract/147/4/blag018/8658411
The species diversity in the family Emeidae of the extinct New Zealand moa (Aves: Dinornithiformes) remains problematic and unresolved because so far there has been little integration of genetic, morphometric, and geographical information underpinned by solid radiocarbon chronologies. Here we re-investigate variation within the genus Euryapteryx using ancient mitochondrial genetics and morphometric analysis of leg bone lengths (femur, tibiotarsus, and tarsometarsus) from samples spanning the entire geographical range of the genus, in geological age from the late Pleistocene to their extinction in the past 1000 years. Our analyses revealed disparity between the results of genetics and morphometrics. We identified geographically distinct phylogenetic lineages, whose distributions were unrelated to morphometric patterns. The morphometric results do not support the current recognition of North and South Island subspecies but are instead consistent with the geographical and climatic histories of populations. This highlights the value of population-level morphometrics in assessing phenotypic response to changing environments, independent of descent. Furthermore, our results underline the value of the unique evolutionary system provided by New Zealand moa in separating the effects of climate, topography, tectonics, and volcanism on the evolution of large vertebrates.
Free pdf:
John Peacock (2026)
Adaptation in the Avian Middle Ear—The Columellar Annular Ligament in Aquatic and Diving Birds
Journal of Morphology 287(4): e70124
doi: https://doi.org/10.1002/jmor.70124
https://onlinelibrary.wiley.com/doi/10.1002/jmor.70124
https://onlinelibrary.wiley.com/doi/epdf/10.1002/jmor.70124
The effective detection of environmental vibrations such as sound waves depends on the transmission of tympanic membrane motion through the middle ear to the inner ear hair cells. In birds, the bony element of the middle ear is the columella; its distal end joins the cartilaginous extracolumella and tympanic membrane, while its basal expansion (the footplate) interfaces with inner ear fluid at the oval window, where it is held in place by the stapedial (columellar) annular ligament. Variation in footplate and oval window geometry can alter the annular ligament's size and shape, thereby influencing middle ear mechanics. Previous studies have noted relatively small footplates in aquatic birds as compared to their terrestrial relatives, and suggested that the adaptive significance of these may relate to their influence on the relative size of the annular ligament. Here, I examine a taxonomically and ecologically broad sample of bird species to test the hypothesis that aquatic lineages have convergently evolved proportionally larger annular ligaments. Results show larger ligaments are characteristic of aquatic, and particularly diving species, while narrower ligaments occur in high-frequency specialists. These patterns are polyphyletic and, alongside their strong ecological associations, indicate repeated functional adaptation of the middle ear. Larger ligaments are consistent with reduced system stiffness and enhanced low-frequency transmission, a hypothesis which is plausible for pelagic seabirds. In contrast, the extreme ligament enlargement in diving taxa is unlikely to be related to hearing, and instead may play a role in protection from barotrauma.
=====
Richard N Holdaway, Morten E Allentoft, Matt J Rayner, Andrea A Cabrera, Alba Rey-Iglesia, Eline D Lorenzen & Michael V Westbury (2026)
Multiproxy analysis of the extinct moa genus Euryapteryx reveals new phylogenetic structure and disparity with morphometrics
Biological Journal of the Linnean Society 147(4): blag018
doi: https://doi.org/10.1093/biolinnean/blag018
https://academic.oup.com/biolinnean/article-abstract/147/4/blag018/8658411
The species diversity in the family Emeidae of the extinct New Zealand moa (Aves: Dinornithiformes) remains problematic and unresolved because so far there has been little integration of genetic, morphometric, and geographical information underpinned by solid radiocarbon chronologies. Here we re-investigate variation within the genus Euryapteryx using ancient mitochondrial genetics and morphometric analysis of leg bone lengths (femur, tibiotarsus, and tarsometarsus) from samples spanning the entire geographical range of the genus, in geological age from the late Pleistocene to their extinction in the past 1000 years. Our analyses revealed disparity between the results of genetics and morphometrics. We identified geographically distinct phylogenetic lineages, whose distributions were unrelated to morphometric patterns. The morphometric results do not support the current recognition of North and South Island subspecies but are instead consistent with the geographical and climatic histories of populations. This highlights the value of population-level morphometrics in assessing phenotypic response to changing environments, independent of descent. Furthermore, our results underline the value of the unique evolutionary system provided by New Zealand moa in separating the effects of climate, topography, tectonics, and volcanism on the evolution of large vertebrates.
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