Not like night and day: the nocturnal letter-winged kite does not differ from diurnal congeners in orbit or endocast morphology
Loading...
Date
2022
Authors
Keirnan, Aubrey
Worthy, Trevor H.
Smaers, Jeroen B.
Mardon, Karine
Iwaniuk, Andrew N.
Wiesbecker, Vera
Journal Title
Journal ISSN
Volume Title
Publisher
The Royal Society Publishing
Abstract
Nocturnal birds display diverse adaptations of the visual system to low-light conditions. The skulls of birds reflect many of these and are used increasingly to infer nocturnality in extinct species. However, it is unclear how reliable such assessments are, particularly in cases of recent evolutionary transitions to nocturnality. Here, we investigate a case of recently evolved nocturnality in the world's only nocturnal hawk, the letter-winged kite Elanus scriptus. We employed phylogenetically informed analyses of orbit, optic foramen and endocast measurements from three-dimensional reconstructions of micro-computed tomography scanned skulls of the letter-winged kite, two congeners, and 13 other accipitrid and falconid raptors. Contrary to earlier suggestions, the letter-winged kite was not unique in any of our metrics. However, all species of Elanus have significantly higher ratios of orbit versus optic foramen diameter, suggesting high visual sensitivity at the expense of acuity. In addition, visual system morphology varies greatly across accipitrid species, likely reflecting hunting styles. Overall, our results suggest that the transition to nocturnality can occur rapidly and without changes to key hard-tissue indicators of vision, but also that hard-tissue anatomy of the visual system may provide a means of inferring a range of raptor behaviours, well beyond nocturnality.
Description
Open access article. Creative Commons Attribution 4.0 International license (CC BY 4.0) applies
Keywords
Letter-winged kite , Nocturnal hawk , Vision , Skull , Evolution , Birds of prey , Elanus scriptus , Nocturnality , Visual system morphology
Citation
Keirnan, A., Worthy, T. H., Smaers, J. B., Mardon, K., Iwaniuk, A. N., & Weisbecker, V. (2022). Not like night and day: The nocturnal letter-winged kite does not differ from diurnal congeners in orbit or endocast morphology. Royal Society Open Science, 9(5), Article 220135. https://doi.org/10.1098/rsos.220135