干旱区生态环境知识资源中心

I studied dispersal of the Barn Owl (Tyto alba) in northern Utah from 1977-96. Based on 144 recoveries of 2085 banded nestlings, the average dispersal distance was 102.9 km (median = 60 km, range = 0-1267 km), occurred in most compass directions from natal sites, but was not random with mountains, deserts, and the Great Salt Lake altering dispersal routes. Dispersal distance was not correlated with severity of winter weather nor population density. Among owls banded as nestlings and recaptured as breeders, females (N = 48) moved significantly farther ((x) over bar = 61.4 km, median = 57.5 km, range = 0-160 km) than males (N = 34, (x) over bar = 35.7 km, median = 14.7 km, range = 0.8-120 km, P = 0.015). Turnover of breeders at nest sites resulted mostly from individuals dispersing into the study area. Only 19 (of at least 500) breeders moved from one breeding site to another. The mean distance moved between breeding sites of 2.3 km (median = 2.25 km) was not significantly different between males and females (P = 0.9), but more females (16) than males (3) made these moves. Eight of the adults that shifted breeding sites did so in the same year either after a failed first attempt (2) or to produce a second brood (6). The remainder changed nest sites in subsequent years.