Size discrimination in barn owls as compared to humans

Abstract

We tested how well barn owls can discriminate objects of different sizes. This ability may be important for the owls when catching prey. We performed a quantitative experiment in the laboratory and trained owls in a task in which the owls had to discriminate whether two rhombi presented simultaneously on a computer monitor were of the same or of different sizes. We obtained full data sets with two experienced owls and one data point with a third owl. For objects being sufficiently larger than the spatial resolution of the barn owl, the angular threshold was related to object size, implying that the discrimination followed Weber's law. The range of Weber fractions we determined was between 0.026 and 0.09. For object sizes close to the spatial resolution, performance degraded. We conducted similar experiments with human subjects. Human thresholds showed the same dependence on object size, albeit down to smaller object sizes. Human performance resulted in a range of Weber fractions extending from 0.025 to 0.036. The differences between owls and humans could be explained by the much higher spatial acuity of humans compared with owls.

New genome assembly of the barn owl (Tyto alba alba)

“…Barn owl adaptation to most ecological conditions (e.g., rain forest, desert, and temperate regions) relies on many notable features such as bill size and plumage color (Romano, Sechaud, Hirzel, & Roulin, ; Romano, Sechaud, & Roulin, ) making this group of bird a relevant biological model. Moreover, as a nocturnal predator, barn owls have developed precise sound localization with asymmetrical ears (Krings, Rosskamp, & Wagner, ), performant sensory information processing (Cazettes, Fischer, Beckert, & Pena, ; Grothe, ; Kraemer, Baxter, Hendrix, & Carr, ), silent flight (Wagner, Weger, Klaas, & Schroder, ), and a great nocturnal visual acuity (Orlowski, Harmening, & Wagner, ; Stemmler et al, ). Barn owls also show a great diversity of color patterns both within and between populations which is related to predator‐prey interactions (San‐Jose et al, ) and signals aspects of individual quality (Roulin & Ducrest, ).…”