Home range, perching height and reaction to approaching humans by radio-tagged Ural Owls.

Abstract

Four breeding Ural Owls (Strix uralensis) (one pair, one female and one male) were radiotagged at the nest and tracked on foot with portable equipment in Hedmark county in SE Norway. The owls´ positions were determined by cross-triangulating or by direct observations. A total of 105 plotted locations were obtained. The mated male and female were located 58 and 22 times on 30 and 17 separate days, respectively, in 1989, while the other female was located 18 times on 15 separate days in 1989, and the other male 7 times on 4 separate days in 1990. From October 1989 on, presumably after the young became independent, the first male moved out of his summer range and eastwards into Sweden. Home range areas were treated as summer areas until this date, and winter areas thereafter. Calculated as 100% minimum convex polygon, the summer (May - September) home range for this male was 11 km2, while his winter (October - December) home range was 63 km2. The corresponding home ranges for his mate were 7 km2 and 20 km2, while for the other female they were 27 km2 and 32 km2. Overall home range for the whole tracking period was 112 km2 for the mated male and 42 km2 for his mate, and 40 km2 for the other female. There was negligible overlap between the home ranges of the two females nesting 8 km apart. A kernel analysis of the male´s summer range data showed that he spent half his activity within an area of 5 km2 around his nest. The owls perched 2.3 - 8 m above ground, with an average of 5.0 m, usually in the lower half of the perch tree. The owls often took off before they were spotted. On the occasions when the owls were seen and flushed, the flight initiation distance ranged 8-35 m, with an average of 20 m. No pellets were found below the perches, and only once was an owl located when ingesting a prey.