I found my first owl nest of the year today. As expected, it was a Great-horned Owl (Bubo virginianus), the species that nests earliest in these parts. The first week of March is late, in fact, for me to be finding my first one. But I've been that busy lately that I haven't had a chance to check some of the likely spots near home, places where GHOWs have nested in years past. The one I found today is at above 6,000 feet of elevation, in an area where winter is still very much in control. The female was sitting tightly on her eggs while snow accumulated on her back.
Owls do not construct their own nests. So when an owl is found to be incubating on a nest of sticks, then that nest was originally constructed by another bird--raven, hawk, or magpie, perhaps--or by a pack rat. The early nesting by these owls often allows them to take over a previous year's Red-tailed Hawk nest (as in this case) before the hawks have returned from wherever they wintered. In my experience, if a pair of Red-tailed Hawks remains on their territory year-round, they generally are able to protect their favorite nest from use by a pair of Great-horned Owls.
At this point in the breeding attempt, I didn't dare approach the nest closely enough to photograph this particular female displaying the faithfulness of a postal employee ("Neither snow nor sleet..."). So instead I've shared below a photo of a different Great-horned Owl fom the same Oregon county and several years ago.