Snowy owls may be active to some extent at both day, from dawn to dusk, and night. Snowy owls have been seen to be active even during the very brief winter daytime in the northern winter. During the Arctic summer, snowy owls may tend to peak in activity during the twilight that is the darkest time available given the lack of full nightfall. Reportedly, the peak time of activity during summer is between 9:00 pm and 3:00 am in Norway. The peak time of activity for those owls that once nested on Fetlar was reported between 10:00 and 11:00 pm. According to one authority, the least active times are at noon and midnight. As days become longer near autumn in Barrow, the snowy owls in the tundra become more active around nightfall and can often be seen resting during the day, especially if it is raining. During winter in Alberta, snowy owls were tracked in the daytime, despite being also active at night (as they were deemed too difficult to track). In the study, they were most active from 8:00-10:00 am and 4:00-6:00 pm and often rested mostly from 10:00 am to 4:00 pm. The owls were perched for 98% of observed daylight and seemed to time their activity to peak times for rodents. The variation of activity is probably in correspondence with their primary prey, the lemmings, and like them, the snowy owl may be considered cathermal. This species can withstand extremely cold temperatures, having been recorded in temperatures as low as minus 62.5 degrees Celsius with no obvious discomfort and also withstood a 5-hour exposure to minus 93 degrees Celsius but may have struggled with oxygen consumption by the end of this period. The snowy owl has perhaps the second lowest thermal conduction to the plumage on average of any bird after only the Adelie penguin (Pygoscelis adeliae) and rivals the best insulated mammals, such as Dall sheep (Ovis dalli) and Arctic fox, as the best insulated polar creature. Presumably as many as 7 rodents would need to be eaten daily to survive an extremely cold winter's day. Adults and young both have been seen to shelter behind rocks to shield themselves from particularly harsh winds or storms. Snowy owls often spending a majority of time on the ground, perched mostly on a slight rise of elevation. It has been interpreted from the morphology of their skeletal structure (i.e. their short, broad legs) that snowy owls are not well-suited to perching extensively in trees or rocks and prefer a flat surface to sit upon. However, they may perch more so in winter though do so only mainly when hunting, at times on hummocks, Fenceposts, telegraph poles by roads, radio and transmission towers, Haystacks, chimneys and the roofs of houses and large buildings. Rocks may be used as perches at times in all seasons. Though often relatively sluggish owls, like most related species, they are capable of sudden dashing movements in various contexts. Snowy owls can walk and run quite quickly, using outstretched wings for balance if necessary. This owl flies with fairly rowing wingbeats, occasionally interrupted by gliding on stretched wings. The flight is fairly buoyant for a Bubo owl. When displaying, the male may engage in an undulating flight with interspersed wingbeats and gliding in a slight dihedral, finally dropping rather vertically to the ground. They are capable for swimming but do not usually do so. Some seen to be swimming were previously injured but young have been seen to swim into water to escape predators if they cannot fly yet. They will also drink when unfrozen water is available. Snowy owl mothers have been observed to preen their young in the wild, while pairs in captivity have been observed to allopreen. In the period leading up to breeding, snowy owls switched regularly between searching (for nesting grounds) and loafing, often searching less when snow cover was less extensive.