First Alpine Swifts at school

Last thursday me and my friends were meeting in front of our school to go to the demonstration (there was a general strike in Spain on thursday 29).
While waiting for my friends a large group of Alpine Swifts flew over the playground.
I guess they'll nest on the building nearby in some ventilation holes like last year.
On the trees on the street I could also find two Serins and a Blackcap.