Snowy Owl hunting behaviour and prey spotting distances revealed by vole lures.

Abstract

When Snowy Owls (Bubo scandiacus) turned up in Finnmark, northern Norway in summer 1993, a vole lure on a line was used to test if the owls would detect, approach and attack the lure in the same way that Great Grey Owls (Strix nebulosa) do (Nero 1980). When a Snowy Owl was spotted more than 100 m away the lure was placed on the ground some 5-10 m away from me. When the owl looked towards me, the line was pulled to make the lure move. The reaction of the owl was observed through a telescope, and noted as positive if the owl stretched and bobbed its head or negative if no obvious reaction could be seen. I was sitting on the ground (n=4) or in a car (n=7) when pulling the lure. A total of 11 tests were carried out between 11-15 July, on nine different individuals (six males, two females, one owl not sexed). All males reacted to the lures from distances up to at least 1 km. The two females did not show any detectable reaction to the lures. Two males approached from at least 500 m and more than 100 m distance and attacked the lure, while another approached from at least 350 m distance to ca 100 m away. A male which sat just over 1 km away detected the lure but did not attack. Movement distances (n=29) were noted for eight undisturbed owls hunting natural prey. These owls most often flew 50-200 m between vantage points (mean 158 m, median 100 m). Short flights of 10-40 m were linked to predation attempts, presumably on lemmings or voles.