Abstract We studied the dispersal patterns of an insular population of California Spotted Owls (Strix occidentalis occidentalis) in southern California from 1987–1998. The study area encompassed the entire San Bernardino Mountains and included a nested, 535-km2 study area which we used to evaluate the effects of study area size on dispersal parameter estimation. One hundred and twenty-nine of the 478 banded juvenile owls (27%) had entered the territorial population by 1998. Over half of the successful dispersers became territorial within one year. Additionally, all females and 95% of the males occupied territories within three years. Twenty-three sibling pairs and one set of triplets dispersed successfully. Sibling dispersal distances were not correlated. Sixty-seven males and 62 females dispersed 2.3–36.4 km (mean ± SD = 10.1 ± 7.6 km) and 0.4–35.7 km (mean ± SD = 11.7 ± 8.1 km), respectively. The difference between male and female mean dispersal distances was not significant. Dispersal distance and firs...