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Recent evidence suggests that frequency of breeding dispersal – the movement from one breeding territory to another – may be increasing in northern spotted owl populations, which could have consequences on population dynamics of this declining species.

Federal and university researchers examined rates and possible causes of breeding dispersal of 4,118 northern spotted owls monitored in Oregon and Washington from 1990 to 2017. The percent of spotted owls dispersing from their territories each year increased by greater than 17 percent during the study. This coincided with a rapid increase in numbers of invasive barred owls as they displaced spotted owls from their preferred breeding sites. Probability of breeding dispersal also increased for single owls and those that had also dispersed the previous year. Spotted owls were less likely to leave high-quality territories with historically high levels of successful reproduction. Findings highlight nuanced interactions between intrinsic and extrinsic factors that contribute to changes in dispersal behavior and population dynamics of an increasingly threatened old-forest species.

Jenkins, J.M., Lesmeister, D.B., Forsman, E.D., Dugger, K.M., Ackers, S.H., Andrews, S., Gremel, S.A., Hollen, B., McCafferty, C.E., Pruett, M.S., Reid, J.A., Sovern, S.G., Wiens, J.D., 2021, Conspecific and congeneric interactions shape increasing rates of breeding dispersal of northern spotted owls: Ecological Applications, no. e02398.

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