Barred Owl Home Range and Habitat Selection in the Boreal Forest of Central Saskatchewan

Abstract

-We assessed Barred Owl (Strix varia) home range and habitat selection in the boreal forest of central Saskatchewan from 1993 to 1995 using radio telemetry (11 females and 4 males). Breeding, nonbreeding, and annual home-range sizes averaged 149, 1,234, and 971 ha, respectively. Breeding and nonbreeding home ranges overlapped entirely for all but two owls. Relative to habitat composition at random areas, Barred Owl breeding home ranges had greater proportions of old (80+ years) mixedwood forest, and nonbreeding home ranges contained greater proportions of old and mature (50 to 79 years) mixedwood and deciduous forest. Both breeding and nonbreeding home ranges contained low proportions of young (<50 years) forest and treed muskeg. Breeding home ranges contained higher proportions of old mixedwood than nonbreeding home ranges. Habitats used for foraging and roosting differed from the proportions of habitat available within the study area. During the breeding period, Barred Owls strongly selected old mixedwood, with lesser selection for mature mixedwood and deciduous forests. Similarly, in the nonbreeding period, old mixedwood was selected most strongly, with lesser selection for mature mixedwood and mature and old deciduous forests. During the breeding period, owls used habitats in proportion to their availability within home ranges, with the exception of young mixedwood forest, which was selected against. Owls selected old mixedwood within their nonbreeding home ranges and avoided young and coniferous forests, treed muskeg, open areas, and water. Received 22 May 1997, accepted 13 February 1998. THE BARRED OWL (Strix varia) is widely distributed in North America, ranging throughout the United States east and north from Texas, across Canada to southeastern Alaska, and south to northern California (Johnsgard 1988). The occurrence of Barred Owls in boreal and western montane forests of Canada and the United States is believed to have resulted from range expansion within the past 100 years (Houston 1959, Taylor and Forsman 1976, Boxall and Stepney 1982, Sharp 1989). This range expansion has brought the Barred Owl into contact with the Spotted Owl (Strix occidentalis) in the northwestern United States, where hybridization has occurred (Hamer et al. 1994). Throughout their range, Barred Owls inhabit a variety of forest types. Numerous authors have suggested that Barred Owls require old forests (Elody and Sloan 1985, Bosakowski et 4Present address: Partners in Flight-Manitoba, Box 24, 200 Saulteaux Crescent, Winnipeg, Manitoba R3J 3W3, Canada. E-mail: kmazur@nr.gov.mb.ca al. 1987, Laidig and Dobkin 1995, Haney 1997, Mazur et al. 1997a). In contrast, the Barred Owl was not considered to be an old-forest obligate by Marcot (1995). In the boreal forest, Barred Owls are associated specifically with old forest (Boxall and Stepney 1982, Dunbar et al. 1991, Van Ael 1996, Mazur et al. 1997a). However, specific habitat selection has not been well quantified in this habitat type. Our objectives were to quantify home-range size and habitat selection by Barred Owls year-round in the boreal forest of central Saskatchewan. Specifically, we wanted to determine whether the Barred Owl is an old-forest obligate within the boreal forest. STUDY AREA AND METHODS The research was conducted from May 1993 to April 1995 within the southern boreal forest of Saskatchewan, Canada (53'55'N, 105?55'W). The study area (ca. 400,000 ha) encompassed the Prince Albert Model Forest, including a portion of Prince Albert N tional Park. The dominant tree species in the