Natal Dispersal of Eastern Screech-Owls

Abstract

Using radiotelemetry we monitored dispersing juvenile Eastern Screech-Owls (Otus asio) in central Kentucky during 1985 and 1986. Juvenile owls (n = 16) from seven families remained on natal territories for an average (±SE) of 55 ± 1.3 days after fledging. The mean dispersal date was 15 July, ranging from 8 to 21 July. The mean number of days between dispersal of the first and last members of a brood was 4.3, ranging from 0 to 9 days. Juveniles (n = 17) dispersed a median distance of 2.3 km from their nest (x̄ = 4.4 ± 1.11 km), ranging from 0.4 to 16.9 km, including one juvenile that continued to use portions of its natal home range. Dispersal distance was not significantly correlated with either dispersal date or the number of days that juveniles remained on natal territories. Mean dispersal direction was 210 ± 99.1°, and the distribution of dispersal angles did not differ significantly from random. After departing from natal areas, individuals (n = 7) settled after an average of 5.6 days, ranging from 2 to 11 days. Mortality of juvenile owls was 18.2% during the period prior to dispersal but increased to 67% after dispersal.