This June 2017 video from a nature reserve in the Murcia region in Spain shows Apus apus, common swifts, at their nest.
Not far from my home is a building which used to be a school, but where artists live and work now.
There used to be a swift nesting colony in the roof of that building. Often, I saw the birds fly and heard them call.
Years ago, the building was restored. Good for the building and its inhabitants. Not good for the swifts; as the colony was gone.
Today, as I walked in that area, ten swifts flying close above my head, calling.