Visual Behaviors in a Laterally-eyed Songbird: European Starlings

Shannon Rhey Butler, Purdue University

Abstract

Animals gather information from their environment to reduce uncertainty and make adaptive decisions, using their sensory system to do so. The configuration of the sensory system can limit the information that an animal can take in, and also influence the behavioral mechanisms that are used to gather it. The goal of this thesis was to characterize the mechanisms that an animal with laterally placed eyes uses to look at (i.e., visually fixate) predators, food, and neighbors. Although visual fixation has been extensively studied in humans and other primates (i.e., animals with frontally placed eyes), fixation strategies in animals with laterally placed eyes (birds, fish, reptiles, etc.) have received considerably less attention. The European starling, a songbird, is a good study species because there is extensive knowledge of its visual system and behaviors. In the first chapter, we characterized a new visual fixation strategy which we labeled monocular alternating fixation. This strategy involves moving the head to make multiple fixations (exposing different parts of the retina to the object of interest) with a single eye before switching to the other eye and repeating the same process. In the second chapter, we asked if starlings could determine where each other is looking (i.e., gaze following). Starlings reoriented their gaze to follow that of a robotic starling around a barrier more often compared to when the robot’s gaze was directed elsewhere, which was the first demonstration of geometric gaze following behavior in a songbird. In the third chapter, we asked (1) whether starlings used their acute (high quality) or peripheral (low quality) vision to monitor their neighbor, and (2) whether starlings mimicked the timing of each other’s visual scanning behaviors or kept them independent. We found that starlings tended to use their retinal periphery rather than their centers of acute vision (high quality vision) to monitor their neighbors. Additionally, we found that starlings did mimic the timing of neighbor’s visual scans, placing them closer together in time than expected by chance. Overall, we found that starlings rely not only on the center of acute vision, but also on other parts of other retina to gather visual

Degree

Ph.D.

Advisors

Fernandez-Juriric, Purdue University.

Subject Area

Ecology

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