I was out for a walk at dusk in nearby Wheelwright Park, and heard a strange sound coming from a nearby tree — a sort of whiny “cheep” kind of sound. I looked up, and there was a juvenile Great Horned Owl about 10 meters up.
The fading light made it hard to see much, but the bird appeared to have well-developed flight feathers. The prominent ear tufts which are characteristic of adult Great Horned Owls were just starting to form. And the plumage was a lighter color than adult plumage. So my guess is that this was a young owl out for one of its first forays from the nest.
As I stood watching it — and trying to take photos with my smartphone — I thought I heard another owl cheeping from a tree farther away. It seems like there were two young owls out trying out their new wings.