Swifts are leaving

The first two swift chicks left box no. 3 two days ago (on 20 July).
The two in box no. 2 will probably leave in the next few days.
Meanwhile the pair in box no. 1 are some weeks behind following the earlier upheavals (see Life with the swifts).
The  clip above shows box no. 1 on 18 July.
IB