Seeing sunlit owls in a new light: orienting Snowy Owls may not be displaying

• Published in: Ibis
• Main Authors: Wiebe, Karen L., Chang, Alexander M.
• Other Authors: Kenneth M. Molson Foundation
• Format: Article in Journal/Newspaper
• Language: English
• Published: Wiley 2017
• Subjects: Canada; Bubo scandiacus
• Online Access: http://dx.doi.org/10.1111/ibi.12533; https://api.wiley.com/onlinelibrary/tdm/v1/articles/10.1111%2Fibi.12533; https://onlinelibrary.wiley.com/doi/pdf/10.1111/ibi.12533

Snowy Owls Bubo scandiacus often face the sun when sitting on the ground or when perched. Such sun‐orienting has been suggested to represent a visual display to conspecifics but other explanations have not been thoroughly examined. We observed the orientation of wintering Snowy Owls to both the sun and the wind, and their perching behaviour during two winters in central Saskatchewan, Canada. We proposed three new explanations for sun orientation in addition to the display hypothesis: thermoregulation, hunting and defence against predators. On sunny days, 44% of 710 Owls faced the sun; this was non‐random because few did so on overcast days. Sun‐ as opposed to wind‐orienting was strongly associated with weather conditions. Logistic regressions indicated that at temperatures below –13 °C and at wind speeds greater than about 18 km/h, Owls tended to orient to the wind rather than to the sun. The likelihood of wind‐orienting increased if the Owl perched above the ground, whereas the likelihood of sun‐orientating increased slightly when the Owl was sitting on the ground. There was no difference between the sexes in orienting behaviour. Snowy Owls seemed to prioritize wind‐orienting for thermoregulation but the results are also consistent with the idea that sun‐orientation can reduce heat loss. Facing into the sun did not support the hunting explanation because the birds would have been blinded and not able to see prey, but was consistent with the protection explanation if it helps to increase vigilance against enemies. Although we cannot completely rule out the display explanation, the spatial context of sunning Owls and a lack of a sex effect makes it unlikely that this is the main function. Instead, Owls seem to trade‐off wind‐ vs. sun‐orienting according to the prevailing weather conditions and do so mainly to thermoregulate and perhaps to maintain vigilance.