USGS and U.S. Forest Service researchers analyzed northern spotted owl natal dispersal, or the distance from natal site to first breeding site, from 1985 – 2012 in Oregon and Washington to examine how barred owls affect northern spotted owls’ movement.
Directional patterns for natal dispersal often coincided with regional distribution of forest habitat and potential dispersal barriers, such as wide valleys. In general, long-distance dispersal was uncommon throughout the study area. However, northern spotted owl natal dispersal in northern ecoregions, where barred owls were more prevalent, was shorter compared to dispersal in southern ecoregions. Researchers also found a decline in age at first breeding over the nearly 20 years studied, coinciding with declining dispersal distances across all ecoregions. These results suggest that northern spotted owls may be trying to improve initial breeding success by attempting to breed earlier in suboptimal territories closer to natal sites, perhaps in response to the scarcity of breeding territories where barred owls are invading.
Hollenbeck, J.P., Haig, S.M., Forsman, E.D., Wiens, J.D., 2018, Geographic variation in natal dispersal of northern spotted owls over 28 years: The Condor, v. 120, no. 3, p. 530-542, https://doi.org/10.1650/CONDOR-17-164.1.
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