Now that the female has moved on from egg-laying-mode to incubation-mode, I've switched off motion detection in favour of live streaming.
It was more of a struggle than I'd expected to get streaming working, but I can now view the action live (well, live-ish if you ignore the 3 second delay) on one or more clients running VLC.
Video can be recorded on the server (i.e. the Raspberry Pi) or on a client.
