It's possible it was a snowy owl my visitor saw. There have been numerous sightings of snowy owls in souther BC this winter, many of them emaciated. Biologists say these are mainly young birds, and it's sad but probably not a major blow to the snowy owl population. Southern migrations are not uncommon. Snowy owls are the largest owls in North America, and they hunt mainly in the daytime.
It turns out what I'm hearing at night, though, is Great Horned Owls. This is the classic "Hoot-hoot ha-oot, hoot hoot," sometimes rendered as "who died today, who, who?" Apparently (according to a comment on YouTube) the First Nations people said this heralded the passing of a soul to the next world.
I must admit, it WAS rather eerie the first time I heard it, but rather than give in to superstition (which I only dimly remembered at that moment anyway) I really listened to the hooting. It's very soft but ringing, and I never hear just one. They're calling to one another, call and response. Sometimes just two, sometimes it seemed to be three or more. They seem to vary the speed and frequency of their calls depending on their distance from one another. If they're far apart, one calls, the other replies, eventually. As they get closer, they reply rapidly, and when they're very near to one another the second owl won't even wait for the first to finish before replying: "Hoot hoot ha-oot -" "Hoot hoot -" "-hoot hoot." "ha-oot hoot hoot." They're finishing one another's sentences.
It turns out this may well be their mating ritual, which happens in winter, and even as early as October. So what I'm hearing is not any sad mourning cry, it's a pickup line!
Much less eerie to listen to as I lie in bed at night.