Meeting Abstract

56.6  Sunday, Jan. 5 14:45  Orbit and Scleral Ring Measurements as Predictors of Diving Ecology BROWNE, K*; CLARKE, J; University of Texas, Austin; University of Texas, Austin katie.pyon@gmail.com

Many birds navigate two optically different media, air and water. A few species, such as penguins (Sphenisciformes) dive to depths approaching the aphotic zone of the ocean and must accommodate their vision to both the change in media and significant light attenuation. Optical properties of the eye e.g., pupil aperture and focal length, are reflected in the eye’s gross morphology and have been shown to have a strong positive correlation with osteological proxies from the orbit and scleral ring. This study combines measurements of osteological features of the eye utilized in previous studies to create a larger feature space for classification of ecology based on eye shape. A total of 170 species were evaluated for distinct classes of eye shape, 97 of which were newly measured species of Charadriiformes, Procellariformes, and Pelecaniformes. Logistic regression and neural networks recovered diving birds as most similar to mesopic terrestrial taxa but did not recover classes by dive depth or activity pattern. Logistic regression recovers different styles of prey capture (i.e., plunge, pursuit, skimming, or wading) based on orbit and scleral ring measurements. Misclassification of dive type is most common in birds that exhibit multiple modes of prey capture. Aquatic birds are active in a wide range of conditions. Foraging both day and night and at varying water depths based on the time of year and available prey. Diverse waterbird ecology probably contributes to the lack of distinct ecological classes based on dive depth and dirunal/nocturnal activity. However, prey capture method has a sufficiently strong influence to allow classification of eye shape with minimal error.