A final update. All of our swifts have now left, with the first youngster in box 3 leaving on Saturday 26th, mid-morning. The second one remained and finally left 3 days later on Tuesday 29th. The adult however came back to roost alone that evening presumably just to make sure that the youngsters were definitely away. Here's a video of the pair of them doing a bit of wing fluttering in preparation for leaving:
This second video was taken in the morning before the first youngster left, you can see they're already looking a bit restless:
And finally, this picture is of the second youngster, rather lonesome, looking out of the box entrance. It was to remain a further 3 days before making the move.
The pair in Box 1 failed to roost on Saturday 26th so we thought they too had left - but they returned again for one night on the Sunday 27th and then left next morning.
So that’s it for this year folks, the end of yet another year and we live in hope that they will all return next year!