Optocollic responses in adult barn owls (Tyto furcata)

Abstract

Barn owls, like primates, have frontally oriented eyes, which allow for a large binocular overlap. While owls have similar binocular vision and visual-search strategies as primates, it is less clear whether reflexive visual behavior also resembles that of primates or is more similar to that of closer related, but lateral-eyed bird species. Test cases are visual responses driven by wide-field movement: the optokinetic, optocollic, and optomotor responses, mediated by eye, head and body movements, respectively. Adult primates have a so-called symmetric horizontal response: they show the same following behavior, if the stimulus, presented to one eye only, moves in the nasal-to-temporal direction or in the temporal-to-nasal direction. By contrast, lateral-eyed birds have an asymmetric response, responding better to temporal-to-nasal movement than to nasal-to-temporal movement. We show here that the horizontal optocollic response of adult barn owls is less asymmetric than that in the chicken for all velocities tested. Moreover, the response is symmetric for low velocities (< 20 deg/s), and similar to that of primates. The response becomes moderately asymmetric for middle-range velocities (20–40 deg/s). A definitive statement for the complex situation for higher velocities (> 40 deg/s) is not possible.

Development of the horizontal optocollic reflex in juvenile barn owls (Tyto furcata pratincola)

“…As in the adult study (Wagner et al 2021), most of our data did not show normal distributions (data not shown). Therefore, we used nonparametric statistics, speci cally the Mann-Whitney U test to analyze the relation of unpaired samples.…”

“…In some cases, we also use the term " rst day of response", meaning the rst PHD at which quantitative data were recorded and the owls responded to the visual stimulus. Optocollic reactions were automatically analyzed with a temporal resolution of 80 msec (for details see Wagner et al 2021). The azimuthal orientation of the owl's head and the azimuthal position of the pattern were synchronously derived and stored for further processing.…”

“…The set-up and the stimuli were the same as in the work with the adult barn owls (Wagner et al 2021). Brie y, visually induced OCRs were elicited with a rotating drum (diameter 64 cm, height 46 cm, angle subtended in elevation 70 as seen from half height) that carried the stimulus pattern.…”

“…Some data sets were also subjected to a correlation analysis, and some to a Wilcoxon matched pairs signed rank test (online program located at https://www.statskingdom.com/175wilcoxon_signed_ranks.html). If we refer to "adult data" in the following we mean the data as published in Wagner et al (2021).…”

“…Mowrer 1936; Gioanni et al 1981; Wallman and Velez 1985) with a higher T-N than N-T gain. The reaction of adult barn owls (Tyto furcata pratincola) is somewhere in between, but closer to that of primates than to that of chickens (Wallman and Velez 1985;Distler et al 1999;Wagner et al 2021). Adult owls have a symmetric hOCR for low stimulus velocities (< 20 deg/s).…”