This dataset contains count and detection-nondetection data of Barred Owls from 106 historical breeding territories of Northern Spotted Owl territories (i.e. sites) in the Oregon Coast Ranges from 1995 to 2016. Data collected from 1995 to 2014 are partitioned into 2-week periods from 1 March - 31 August each year, totaling 12 possible sampling periods per year. Data collected from 2015 and 2016 are partitioned into 2-month periods from 1 March - 31 August, totaling 3 possible sampling periods each year. This dataset also describes the proportion of total area surveyed per site per sampling period in 2015 and 2016, as well as the proportion of each site with older coniferous forest in each year (1995 - 2016).