My old friend Hempenstein sent this video, and at first I couldn’t figure out what was going on: I thought the owlet nestlings were listening for their mother. But then I realized that they were following a fly that was loose in the nest box. As Hempenstein commented on the video:
Jesus they’re strange-looking, but 2+ min of them is somehow fascinating to watch.
They are of course barn owls (Tyto alba).