In the meantime ...

So far so good. If I must believe the yahoo lists, I'm very fortunate, some persons have not yet seen anything while I can claim to have seen them almost every day.
21 April, I went back to Apus College and saw 7 and finally one flew into a nest. Not a nestbox, but where the roof and wall meets. The building is old and has lots of secret places for swifts to nest. This swift I have seen before as one of the early arrivals. First time I saw it I was not sure I really saw it and when I went back the next day, I kept watching that place and indeed it flew into it. Early bird!
The same evening I saw another swift flew into a nestbox at 71 Plein street.
Already 2 coming home!
24 April, I heard them for the first time while working in the garden!
25 April I stood out in the street before my house and saw 2, then 5 and then another 2.
30 April, while planting flowers I bought earlier, I heard them above me and when I went outside - unfortunately to see my boxes I must stand outside in the street - I saw straight away numerous swifts flying. They were not high, not drifting off to a distant destination, they were in the area known to them. The weather was much warmer and not windy, just right for them to play in the sky above home territory.
At about 20:35 I saw one flew in at 10 Rega street. It needed a second time round to find the right angle.
1 May the weather was not so pleasant as the day before, a rather cold wind was blowing through the street. Even on beautiful days there can be a cold draft, you only get to know all these inconvenientcies when you've stood long enough waiting and watching swifts.
Mine are not back yet.