Strix varia

Dense woodland and forest (coniferous or hardwood), swamps, wooded river valleys, cabbage palm-live oak hammocks; often in areas bordering streams, marshes, and meadows (AOU 1983), but also commonly in upland areas; habitat use reflects vegetation characteristics rather than proximity of water per se. Generally in expansive forested area with large mature and decadent trees that provide cavities suitable for security and nesting (Allen 1987). Appears to prefer older stands but uses earlier stages of forest succession if enough large trees or snags (or nest boxes) are present (Allen 1987). Often in forests with relatively open understory. Prefers canopy closure of 60% or greater. Often replaced by the great horned owl in fragmented open forests.

Nests in tree cavity, in abandoned nest of squirrel, crow, or hawk, or in top of hollow tree stub, usually at least 7-8 m above ground. Uses both living and dead trees. Trees with cavity suitable for nesting generally at least 51 cm DBH; habitat suitability index model assumes that a density of at least 2 stems of this diameter per 0.4 ha represents high quality habitat for reproduction; high quality reproductive habitat also indicated by canopy cover of overstory trees of 60% or more (Allen 1987). Nest sites typically used in successive years.

Home range usually is less than 400 ha (but up to 760 ha) over 2-7 months in Minnesota, average 273 hectares; usually no overlap except in mated pair; boundaries generally are constant from year to year (Nicholls and Warner 1972). Annual home range averaged 282 hectares in Michigan (Elody and Sloan 1985) and 971 hectares in Saskatchewan (Mazur et al. 1998). Reported density: 0.03-1.0 pairs/sq km.

Expanding populations in Pacific Northwest could threaten spotted owl through competiton and/or hybridization (see Hamer et al. 1994).

Egg dates: late March-May in southern New England, late February-April in New Jersey, Illinois, and Iowa, January-March in Florida. Nesting peaks from early March to early May in Maryland (see Bushman and Therres 1988). Clutch size usually is 2-3. Incubation lasts 28-33 days. Young may leave nest at 4-5 weeks, fly at 6 weeks, may still receive some food from parents at 4 months.